Ground Electrical Path From An MLCC Filter Capacitor On An AIMD Circuit Board To The Ferrule Of A Hermetic Feedthrough

ABSTRACT

An EMI/energy dissipating filter for an active implantable medical device (AIMD) is described. The filter comprises a first gold braze hermetically sealing the insulator to a ferrule that is configured to be mounted in an opening in a housing for the AIMD. A lead wire is hermetically sealed in a passageway through the insulator by a second gold braze. A circuit board substrate is disposed adjacent the insulator. A two-terminal chip capacitor disposed adjacent to the circuit board has an active end metallization that is electrically connected to the active electrode plates and a ground end metallization that is electrically connected to the at least one ground electrode plates of the chip capacitor. There is a ground path electrically extending between the ground end metallization of the chip capacitor and the ferrule. The ground path comprises at least a first electrical connection material connected directly to the first gold braze, and at least an internal ground plate disposed within the circuit board substrate with the internal ground plate being electrically connected to both the first electrical connection material and the ground end metallization of the chip capacitor. An active path electrically extends between the active end metallization of the chip capacitor and the lead wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/452,785,filed on Jun. 26, 2019, now U.S. Pat. No. 11,147,977, which is acontinuation-in-part of U.S. patent application Ser. No. 16/435,600,filed on Jun. 10, 2019, which is a continuation application of U.S.patent application Ser. No. 16/385,338, filed on Apr. 16, 2019, now U.S.Pat. No. 10,874,866, which is a continuation application of U.S. patentapplication Ser. No. 16/364,953, filed on Mar. 26, 2019, now U.S. Pat.No. 10,857,369, which is a continuation application of U.S. patentapplication Ser. No. 16/045,035, filed on Jul. 25, 2018, now U.S. Pat.No. 11,013,928, which is a continuation application of U.S. patentapplication Ser. No. 15/651,045, filed on Jul. 17, 2017, now U.S. Pat.No. 10,124,164, which is a continuation application of U.S. patentapplication Ser. No. 14/503,583, filed on Oct. 1, 2014, abandoned, whichis a divisional application of U.S. patent application Ser. No.13/873,832, filed on Apr. 30, 2013, now U.S. Pat. No. 8,868,189, whichis a continuation application of U.S. patent application Ser. No.13/528,052, filed on Jun. 20, 2012, now U.S. Pat. No. 8,433,410, whichis a continuation application of U.S. patent application Ser. No.12/407,402, filed on Mar. 19, 2009, now U.S. Pat. No. 8,195,295, whichclaims priority from U.S. Provisional Pat. App. Ser. No. 61/038,382,filed on Mar. 20, 2008; 61/116,094, filed on Nov. 19, 2008; 61/144,102,filed on Jan. 12, 2009; and 61/150,061, filed on Feb. 5, 2009, thecontents of which are fully incorporated herein with this reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to feedthrough filter capacitorEMI filters. More particularly, the present invention relates to ahybrid EMI filter substrate and/or flex cable assembly which embodiesembedded shielded flat-through/feedthrough filters and/or energydissipating circuit elements. This invention is applicable to a widerange of connectors, terminals and/or hermetic seals that support leadwires as they ingress/egress into electronic modules or shieldedhousings. In particular, the present invention applies to a wide varietyof active implantable medical devices (AIMDs).

FIGS. 1-40 provide a background for better understanding thesignificance and novelty of the present invention.

FIG. 1 illustrates various types of active implantable and externalmedical deVices 100 that are currently in use. FIG. 1 is a wire formeddiagram of a generic human body showing a number of implanted medicaldevices. 100A represents a family of hearing devices which can includethe group of cochlear implants, piezoelectric sound bridge transducersand the like. 100B represents a variety of neurostimulators and brainstimulators. Neurostimulators are used to stimulate the Vagus nerve, forexample, to treat epilepsy, obesity and depression.

Brain stimulators are pacemaker-like devices and include electrodesimplanted deep into the brain for sensing the onset of the seizure andalso providing electrical stimulation to brain tissue to prevent theseizure from actually occurring. The lead wires associated with a deepbrain stimulator are often placed using real time MRI imaging. 100Cshows a cardiac pacemaker which is well-known in the art. 100D includesthe family of left ventricular assist devices (LVAD's), and artificialhearts, including the recently introduced artificial heart known as theAbiocor. 100E includes an entire family of drug pumps which can be usedfor dispensing of insulin, chemotherapy drugs, pain medications and thelike. Insulin pumps are evolving from passive devices to ones that havesensors and closed loop systems. That is, real time monitoring of bloodsugar levels will occur. These devices tend to be more sensitive to EMIthan passive pumps that have no sense circuitry or externally implantedlead wires. 100F includes a variety of bone growth stimulators for rapidhealing of fractures. 100G includes urinary incontinence devices. 100Hincludes the family of pain relief spinal cord stimulators andanti-tremor stimulators. 100H also includes an entire family of othertypes of neurostimulators used to block pain. 100I includes a family ofimplantable cardioverter defibrillator (ICD) devices and also includesthe family of congestive heart failure devices (CHF). This is also knownin the art as cardio resynchronization therapy devices, otherwise knownas CRT devices. 100J illustrates an externally worn pack. This packcould be an external insulin pump, an external drug pump, an externalneurostimulator or even a ventricular assist device. 100K illustratesthe insertion of an external probe or catheter. These probes can beinserted into the femoral artery, for example, or in any other number oflocations in the human body. 1001.. illustrates one of various types ofEKG/ECG external skin electrodes which can be placed at variouslocations. 100M are external EEG electrodes placed on the head.

FIG. 2 is a prior art unipolar discoidal feedthrough capacitor, whichhas an active internal electrode plate set 102 and a ground electrodeplate set 104. The inside diameter termination surface 106 is connectedelectrically to the active electrode plate set 102. An outside diametertermination surface 108 is both solderable and electrically conductive,and it is connected to the outside diameter of electrode plate sets 104.

FIG. 3 is a cross-section of the discoidal feedthrough capacitor of FIG.2 shown mounted to a hermetic seal 112 of an active implantable medicaldevice (AIMD). In prior art discoidal feedthrough capacitor devices, thelead wire 114 is continuous. The hermetic seal 112 is attached to,typically, a titanium housing 116, for example, of a cardiac pacemaker.An insulator 118, like alumina ceramic or glass, is disposed within aferrule 120 and forms a hermetic seal against body fluids. The terminalpin or lead wire 114 extends through the hermetic seal 112, passingthrough aligned passageways through the insulator 118 and the capacitor110. A gold braze 122 forms a hermetic seal joint between the terminalpin 114 and the insulator 118. Another gold braze 124 forms a hermeticseal joint between the alumina insulator 118 and the titanium ferrule120. A laser weld 126 provides a hermetic seal joint between the ferrule120 and the housing 116. The feedthrough capacitor 110 is shown surfacemounted in accordance with U.S. Pat. No. 5,333,095, and has anelectrical connection 128 between its inside diameter metallization 106and hence the active electrode plate set 102 and lead wire 114. There isalso an outside diameter electrical connection 130 which connects thecapacitor's outside diameter metallization 108 and hence the groundelectrodes 104 to the ferrule 120. Feedthrough capacitors are veryefficient high frequency devices that have minimal series inductance.This allows them to operate as EMI filters over very broad frequencyranges. Referring once again to FIG. 3, one can see that another way todescribe a prior art discoidal feedthrough capacitor 110 is as athree-terminal capacitor. Three-terminal devices generally act astransmission lines. Referring to FIG. 3, one can see that there is acurrent “I” that passes into lead wire 114. For a prior art AIMD, on thebody fluid side there is generally an implanted lead which canundesirably act as an antenna which can pick up energy fromenvironmental emitters. This energy is known as electromagneticinterference (EMI). Cell phones, microwave ovens and the like have allbeen implicated in causing interference with active implantable medicaldevices. If this interference enters lead wire 114 at point X (FIG. 3),it is attenuated along its length by the feedthrough capacitor 110. Uponexiting, the undesirable high frequency EMI has been cleaned off of thenormal low frequency (LF) circuit current (such as pacemaker pacingpulses or biologic frequency sensors) so that the high frequency EMI hasbeen significantly attenuated. Another way of looking at this is as thehigh frequency energy passes from terminal 1 to terminal 2 (FIGS. 3 and4), it is diverted through the feedthrough capacitor 110 to the groundterminal which is also known as the third terminal or terminal 3. Thefeedthrough capacitor 110 also performs two other important functions:a) its internal electrodes 102 and 104 act as a continuous part of theoverall electromagnetic shield housing of the electronic device ormodule which physically blocks direct entry of high frequency RF energythrough the hermetic seal 112 or equivalent opening for lead wireingress and egress in the otherwise completely shielded housing (such RFenergy, if it does penetrate inside the shielded housing can couple toand interfere with sensitive electronic circuitry), and; b) thefeedthrough capacitor 110 very effectively shunts undesired highfrequency EMI signals off of the lead wires to the overall shieldhousing where such energy is dissipated in eddy currents resulting in avery small temperature rise.

FIG. 4 is a schematic diagram showing the discoidal feedthroughcapacitor 110 previously described in connection with FIGS. 2 and 3. Asone can see, it is a three-terminal device consistent with terminals 1,2 and 3 illustrated in FIG. 3.

FIG. 5 is a quadpolar prior art feedthrough capacitor 132 which issimilar in construction to that previously described in FIG. 2 exceptthat it has four through holes.

Throughout this description, functionally equivalent elements will begiven the same reference number, irrespective of the embodiment beingshown.

FIG. 6 is a cross-section showing the internal electrodes 102, 104 ofthe capacitor 132 of FIG. 5.

FIG. 7 is a schematic diagram showing the four discrete feedthroughcapacitors comprising the quadpolar feedthrough capacitor 132 of FIGS. 5and 6.

FIG. 8 is an exploded electrode view showing the inner and outerdiameter electrodes of the unipolar feedthrough capacitor 110 of FIGS. 2and 3. One can see the active electrode plates set 102 and the groundelectrode plate set 104. Cover layers 134 are put on the top and bottomfor added electrical installation and mechanical strength.

FIG. 9 is an exploded view of the interior electrodes of the prior artquadpolar feedthrough capacitor 132 previously illustrated in FIG. 5. Asshown in FIG. 9, the active electrode plate sets are shown as 102 andthe ground electrode plates are shown as 104. Cover layers 134 serve thesame purpose as previously described in connection with FIG. 8.

FIG. 10 illustrates a prior art quadpolar feedthrough capacitor 132mounted on top of a hermetic insulator 118 wherein a wire bond substrate136 is attached to the top as shown. Wire bond pads 138, 138′, 138″,138′″ and 140 are shown for convenient connection to the internalcircuitry of the AIMD. This is more thoroughly described in FIGS. 75 and76 of U.S. Pat. Nos. 7,038,900 and 7,310,216, the contents of which areincorporated herein.

FIG. 11 is a cross-section taken generally from section 11-11 from FIG.10. In FIG. 11, the internal circuit traces T₁ through T₄ to the wirebond pads 138-138′″ are shown. Referring back to FIG. 10, there is anadditional wire bond pad 140 shown on the left side of the wire bondsubstrate 136. This is also shown in FIG. 11. This is a groundconnection to the outside diameter of the hermetic seal ferrule 120 andprovides a convenient connection point for electronic circuits and thelike that need a ground attachment point on the inside of the AIMD.

FIG. 12 is a schematic diagram of the prior art wire bond pad quadpolarhermetic feedthrough 132 of FIG. 10.

FIG. 13 is a prior art monolithic ceramic capacitor (MLCC) 142. Theseare made by the hundreds of millions per day to service the consumerelectronics and other markets. Virtually all cell phones and other typesof electronic devices have many of these. In FIG. 13, one can see thatthe MLCC 142 has a body 144 generally consisting of a high dielectricconstant ceramic such as barium titanate. It also has solderabletermination surfaces 146 and 148 at either end. These terminationsurfaces 146 and 148 provide a convenient way to make a connection tothe internal electrode plates of the MLCC capacitor 142. FIG. 13 canalso take the shape and characteristics of a number of other types ofcapacitor technologies, including rectangular, cylindrical, round,tantalum, aluminum electrolytic, stacked film or any other type ofcapacitor technology.

FIG. 14 is a sectional view taken from section 14-14 in FIG. 13. Theleft hand electrode plate set is shown as 150 and the right handelectrode plate set is shown as 152. One can see that the left handelectrode plates 150 are electrically connected to the externalmetallization surface 146. The opposite electrode plate set (or righthand plate set) 152 is shown connected to the external metallizationsurface 148. One can see that prior art MLCC and equivalent chipcapacitors are also known as two-terminal capacitors. That is, there areonly two ways electrical energy can connect to the body of thecapacitor. In FIGS. 13 and 14, the first terminal “1” is on the leftside and the second terminal “2” is on the right side.

FIG. 15 is an ideal schematic diagram of the prior art MLCC capacitor142 of FIG. 13.

FIG. 16 is a more realistic schematic diagram showing the fact that theMLCC 142 structure as illustrated in FIG. 13 has series inductance L.This inductive property arises from the fact that it is a two-terminaldevice and does not act as a transmission line. That is, its lead wiresand associated internal electrodes all tend to add series inductance tothe capacitor. It is well known to electrical engineers that MLCCcapacitors will self-resonate at a particular frequency. FIG. 17 givesthe formula for this resonant frequency. There is always a point atwhich the capacitive reactance as shown in FIG. 16 is equal and oppositeto the inductive reactance. It is this point that these two imaginarycomponents cancel each other out. If it weren't for resistive losses, atthe resonant frequency the impedance between 146,1 and 148,2 as shown inFIG. 16 would go to zero. However, the resistive losses of the inductorL and the equivalent series resistance of the capacitor C prevent thisfrom happening. This is better understood by referring to FIG. 18.

Shown in FIG. 18 are three curves. An ideal capacitor curve is shownwhich is very similar to the response of a feedthrough capacitor, suchas shown in FIG. 3. One can see that the attenuation goes up fairlylinearly with frequency all the way up to very high frequencies evenabove 10,000 megahertz (MHz). The MLCC curve is for the capacitor ofFIG. 13. At low frequencies, in this case below 100 MHz, the MLCC curvetracks very closely to an ideal or a feedthrough capacitor. However, asthe MLCC nears its self-resonant frequency (SRF), its attenuation tendsto go up dramatically. This is because when one refers back to FIG. 16,the inductive and capacitive reactance elements are tending to canceleach other out. As previously mentioned, if it weren't for its resistivelosses at resonance (SRF), the MLCC chip would look like a shortcircuit, in which ideal case its attenuation would be infinite. Thismeans that if it weren't for these resistive losses, we would haveinfinite attenuation at the SRF. Instead what we have is a peak ofapproximately 60 dB as shown. Above resonance, the MLCC capacitorbecomes increasingly inductive and the attenuation drops dramatically.This is an undesirable effect and this is why feedthrough capacitorshave generally been the preferred choice for use in EMI broadbandfilters.

FIG. 19 shows three different size MLCC capacitors C₁-C₃ connectedaround a unipolar feedthrough pin or lead wire 114. Self-resonantfrequency is dependent upon the internal inductance of a capacitor. Thiswas illustrated and described in connection with FIG. 16. One can reducethe amount of inductance by using a physically smaller MLCC capacitor.For example, referring to FIG. 19, one could have one each of what isknown in the art as a size 0402, a 0603 and a 0805 MLCC capacitor. Thisis an EIA designation wherein, for example, 0805 would be 0.080 incheslong and 0.050 inches wide. Accordingly, these three MLCC capacitorsC₁-C₃ would have three different resonant frequencies. This is morethoroughly described in U.S. Pat. Nos. 5,973,907 and 5,959,336 thecontents of which are incorporated herein by reference. FIG. 20 is theschematic diagram for the three MLCC capacitors of FIG. 19.

FIG. 21 shows the attenuation response for the three chip capacitorunipolar hermetic terminal in FIG. 19. These three capacitors C₁-C₃ areacting in parallel as shown in the schematic diagram of FIG. 20.Referring to FIG. 21, we can see that there are now three resonant peaksrepresenting the self-resonant frequency of each of these individualMLCC capacitors acting together in parallel. Shown for reference is theideal capacitor response curve previously shown in FIG. 18. The SRF forC₁, C₂ and C₃ are also shown. The physically largest capacitor C₁ willhave the lowest self-resonant frequency whereas the physically smallercapacitor (C₃) will have the highest self-resonant frequency. This isbecause, in general, the smaller the MLCC capacitor, the lower itsinternal inductance. Secondary factors that determine the value of theundesirable equivalent series inductance (ESL) of an MLCC capacitorinclude the number and spacing of internal electrodes, geometry, formfactor and circuit board mounting techniques.

Referring once again to FIG. 19, the reason why this approach has neverbeen commonly practiced in the AIMD market is the fact that this is acomplicated design and is also costly. Because of the space limitationsand reliability implications, packing this many components into such asmall place becomes impractical.

FIG. 22 shows a different method of mounting MLCC capacitors, forexample, those previously shown in FIG. 19. In the industry, this isknown as the tombstone mounting position, which is a highly undesirablething to do when the capacitor is to be used as an EMI filter or an RFdecoupling device (bad mounting and bad form factor). This is becausethe capacitor's inductive loop area L₁ tends to increase. The increasedinductive loop area (integral of area bounded under the loop) has theeffect of directly raising the inductance L as previously described inconnection with FIG. 16. The reason this is undesirable is thisparticular capacitor will tend to self-resonate at a much lowerfrequency (and thereby becomes a less effective high frequency device orEMI filter).

FIG. 23 illustrates a more desirable way to mount the MLCC capacitor 142of FIG. 22. This is a conventional flat surface mount technique, whichhas a much lower inductive loop area L₂ as shown (area bounded under theloop). Accordingly, even though the two capacitors are identical in sizeand capacitance value, the MLCC capacitor 142 as shown in FIG. 23 willresonate ata much higher frequency before it starts to becomeundesirably inductive.

FIG. 24 is known in the art as a reverse geometry MLCC capacitor 142′.For comparative purposes, the physical size of the MLCC capacitorillustrated in FIG. 24 is exactly the same dimensions as the MLCCcapacitors 142 previously shown in FIGS. 22 and 23. The important thingis the location of the termination surfaces 146′ and 148′. The MLCCcapacitor 142′ in FIG. 24 has been terminated along its long sides.Accordingly, its inductive loop area or the area bounded underneath theloop L₃ is the smallest of all the loop configurations. Thus, thecapacitor 142′ of FIG. 24 will self-resonate at a much higher frequencyas compared to the MLCC capacitors 142 shown in FIGS. 22 and 23. A goodtreatment of this is found in a technical paper entitled, A CAPACITOR'SINDUCTANCE, which was given at the Capacitor and Resistor TechnologySymposium in Lisbon, Portugal, Oct. 19-22, 1999. This paper wasco-authored by Robert Stevenson and Dr. Gary Ewell of AerospaceCorporation. A related paper was given entitled, A CAPACITOR'SINDUCTANCE: CRITICAL PROPERTY FOR CERTAIN APPLICATIONS and was given bythe same authors at the 49.sup.th Electronic and Components TechnologyConference of the Institute of Electrical and Electronic Engineers heldJun. 1-4, 1999 in San Diego, Calif.

FIG. 25 is the same electrical schematic diagram as previouslyillustrated in FIG. 16, but additionally showing the equivalent circuitmodel for an MLCC. Added are resistors IR and ESR. IR is the insulationresistance of the capacitor C. For electronic circuit analysis reasons,this IR resistor can generally be ignored. The reason for this is thatit is typical that the value of IR is in excess of 10 Gigaohms(10,000,000,000 ohms). This number is so high compared to the values ofthe other components of the capacitor circuit model that it can besafely ignored. Also added to the complete schematic model shown in FIG.25 is the capacitor series resistance (ESR). This is the total ESRincluding the dielectric loss tangent of the ceramic materialsthemselves and all ohmic losses and other electrical connections withinand external to the capacitor itself. As previously stated, the presenceof resistor ESR is why at the self-resonant frequency, the insertionloss does not go to infinity.

FIG. 26 is a prior art chip transient suppression diode 154, such as atransorb or the like.

FIG. 27 is a schematic diagram showing the diode chip 154 of FIG. 26connected between an active medical device lead wire 114 and circuitground. The dashed line shown in FIG. 27 illustrates the shieldedhousing of the AIMD. The reason for diode chip 154 (or multiple diodearrays) is to help protect the sensitive electronic circuits of the AIMDfrom external high voltage insults. These could be electrostaticdischarges or the application to the patient of automatic (high voltage)external defibrillation (AED). AEDs are commonly now found in governmentbuildings, airports, airplanes and the like. It is very important that apacemaker not be burned out during the application of an AED externaldefibrillation event. The diode chip 154 shown in FIGS. 26 and 27basically is typically an avalanche type diode which is also known inthe art as a zener diode. In other words, they do not forward bias orshort out until a certain voltage threshold is reached. These are alsoknown in the art as transorbs and also have other market names. Suchdiodes can be back to back and placed in parallel in order to suppressbiphasic high voltage AED defibrillation pulses.

FIG. 28 is a prior art inductor chip 156. There are many manufacturersof these. These can either have ferrite elements or benon-ferromagnetic. They come in a variety of sizes, inductance valuesand voltage ratings.

FIG. 29 is a schematic diagram of the inductor chip 156 of FIG. 28.

Referring to FIG. 30, one can see that an inductor circuit trace 158 isprinted or deposited right on top of a prior art MLCC capacitor 142 toform an MLCC-T 160. The advantage here is that low cost MLCC's whichhave been produced from very high volume commercial capacitor operationscould be utilized and the inductor trace 158 could be printed on as asupplemental operation. This forms a parallel inductor (L)-capacitor (C)resonant L-C circuit which creates a very high impedance at its resonantfrequency. This is effective for suppressing a single RF frequency, suchas that from Magnetic Resonance Imaging (MRI) equipment, or the like.This is more thoroughly described in U.S. Patent Application PublicationNo. US 2007-0112398 A1, the contents of which are incorporated herein byreference.

FIG. 31 shows yet another way to deposit an inductor shape 158 onto aseparate substrate 162 to form a parallel L-C resonant circuit. Forexample, the substrate 162 could be of alumina ceramic or other suitablecircuit board material. This could then be bonded with a thin adhesivelayer 164 to a prior art MLCC capacitor 142. The composite MLCC-Tstructure 160′, including corresponding metallization surfaces 146 and148 on opposite ends, is illustrated in the electrical schematic diagramof FIG. 34 where it is evident that the structure forms a parallel L andC “tank” or bandstop circuit.

FIG. 32 is an isometric view of a novel composite monolithic ceramiccapacitor-parallel resonant tank (MLCC-T) 160″ which forms a bandstop ortank filter 166 in accordance with previously referenced U.S. patentapplication Ser. No. 11/558,349. Viewed externally, one can see nodifference between the MLCC-T 160″ of the present invention and priorart MLCC capacitor 142 as shown in FIG. 13. However, the novel MLCC-T160″ has an embedded inductor 162 which is connected in parallel acrossthe capacitor between its opposite termination surfaces 146 and 148.

FIG. 33 illustrates an exploded view of the various layers of the novelMLCC-T tank filter 160″ shown in FIG. 32. The novel MLCC tank (MLCC-T)160″ includes an embedded inductor 162. At low frequencies, the embeddedinductor 162 shorts out the capacitor from one end to the other.However, at high frequency, this forms a parallel tank circuit 166 whichis again better understood by referring to the schematic diagram in FIG.34. Referring once again to FIG. 33, one can see that as the capacitorstacks up from the top, we have an area of blank cover sheets 168followed by one or more embedded inductor layers 162. These inductortraces can have a variety of shapes as further illustrated in FIG. 83 ofU.S. Patent Application Publication No. US 2007-0112398 A1. It will beobvious to those skilled in the art that there are a variety of optionalshapes that could also be used. Then there are a number of other blankinterleafs 170 before one gets to the capacitor electrode plate sets,150 and 152. One can see the capacitor electrode plate set 150 whichconnects to the left hand termination 146 and one can also see thecapacitor electrode plate set 152 which connects to the right handtermination 148. In FIG. 33, only single electrodes are shown as 150,152. However, it will be obvious to those skilled in the art that anynumber of plates “n” could be stacked up to form the capacitance valuethat is desired. Then bottom blank cover sheets 168 are added to provideinsulative and mechanical strength to the overall TANK filter MLCC-T160″.

After sintering the composite structure at high temperature, the laststep, referring back to FIG. 32, is the application of the solderabletermination surfaces 146 and 148. These termination surfaces can be athick film ink, such as palladium silver, glass frit, gold plating, orthe like and applied in many processes that are known in the art. Onceagain, the overall MLCC-T 160″, which is illustrated in FIG. 32, looksidentical to a prior art MLCC 142 as shown in FIG. 13. However, embeddedwithin it is a novel parallel inductor structure 162 creating a novelparallel tank or bandstop filter 166 shown in the schematic diagram ofFIG. 34.

Referring to schematic drawing FIG. 34, one can see that the inductor Lhas been placed in parallel with the capacitor C which is allconveniently located within the monolithic structure MLCC-T 160″ shownin FIG. 32.

In FIG. 35 only one pole of a quadpolar feedthrough capacitor 132 isshown, which is better understood by referring to its schematic diagramshown in FIG. 36. One can see that there is a feedthrough capacitor 132which is also known as a broadband EMI filter shown as C₁, C₂, C₃ and C₄in FIG. 36. In line with each one of these circuits is a parallelresonant bandstop filter MLCC-T 160 to block MRI pulsed RF frequenciesor frequencies from similar powerful emitters. The function of thesebandstop filters is better understood by referring to the completedescription in U.S. Pat. No. 7,363,090, the contents of which areincorporated herein.

Referring once again to FIG. 35, one can see that there is a metallicferrule 120 which is attached to a hermetic insulator 118 by means ofgold braze 124. There are also two lead wires 114 and 114′ as shown.Lead wire 114 is mechanically and hermetically attached to insulator 118by means of gold braze material 122. The bandstop filter or tank filterMLCC-T 160 is held in place with an insulative spacer plate 172. Thefeedthrough capacitor 132 is mounted on top as shown. Lead wire 114′ isattached to the other end of the tank filter MLCC-T 160. A capacitoroutside diameter metallization 108 connects to the capacitor's internalground electrodes 104. Electrical connection 126 is made between thecapacitor's outside diameter metallization 108 and both the metal of theferrule 120 and gold braze material 124.

FIG. 37 is a different type of prior art MLCC feedthrough capacitor 142that is built into a special configuration. It is known in the art bysome as a flat-through capacitor (it also has other trade names). Itwill be referred to herein as a flat-through capacitor 174. At lowfrequencies, the flat-through capacitor 174 exhibits ideal capacitancebehavior versus frequency. That is, its attenuation curve versusfrequency is nearly ideal. This is because it is truly a three-terminaldevice which acts as a transmission line in a manner similar to those ofprior art discoidal feedthrough capacitors 110. This is betterunderstood by referring to its internal electrode plate geometry asshown in FIG. 38. Shown is a through or active electrode plate 175 thatis sandwiched between two ground electrode plates 178 and 178′. Thethrough or active electrode plate 175 is connected at both ends bytermination surfaces 180 and 182. When the capacitor is mounted betweencircuit trace lands 184 and 186 as shown in FIG. 37, this connects thecircuit trace together between points 184 and 186. Referring to theactive circuit trace 175 in FIG. 38, one can see that there is a currenti₁ that enters. If this is a high frequency EMI current, it will beattenuated along its length by the capacitance of the flat-throughcapacitor and emerge as a much smaller in amplitude EMI signal atterminal 2 as i_(1′). Similar to discoidal feedthrough capacitors, theflat-through capacitor 174 is also a three-terminal capacitor asillustrated in FIG. 37. The point of current input i₁ is terminal 1, thepoint of circuit current egress i_(1′) is known as terminal 2 and groundis known as terminal 3. In other words, any RF currents that are flowingdown the circuit trace must pass through the electrodes 175 of thecapacitor 174. This means that any RF signals are exposed for the fulllength of the electrode plate 175 between the ground electrodes 178 andthe capacitance that is formed between them. This has the effect ofmaking a very novel shape for a three-terminal feedthrough capacitor.One negative to this type of capacitor 174 is that it is notconveniently mountable in such a way that it becomes an integral part ofan overall shield. There is always a frequency at which undesirable RFcoupling 188 across the device will occur. This usually does not happenuntil 100 MHz or above. At very high frequencies, such as above 1 GHz,this problem becomes quite serious. Another negative, as compared toprior art discoidal feedthrough capacitors 110 (where the circuitcurrent passes through a robust lead in a feedthrough hole), is that theflat-through capacitor circuit currents must flow through the electrodesof the flat-through capacitor itself (in prior art discoldalifeedthroughcapacitors, the only current that flows in the electrodes is highfrequency EMI currents). Monolithic ceramic manufacturing limitations onelectrode thickness and conductivity means that prior art flat-throughcapacitors 174 have relatively high series resistance and can only berated to a few hundred milliamps or a few amps at best (however, animplantable defibrillator must deliver a high voltage pulse of over20-amps). Prior art MLCC and flat-through electrodes must be keptrelatively thin to promote ceramic grain growth through the electrodesin order to keep the capacitor layers from delaminating duringmanufacturing or worse yet, during subsequent mechanical or thermalshocks which can cause latent failures.

FIG. 39 is the schematic diagram of the prior art flat-through capacitor174 as illustrated in FIG. 37. Note that its schematic diagram is thesame as that for the feedthrough capacitor 110 shown in FIGS. 2 and 3.The difference is that feedthrough capacitors are inherently configuredto be mounted as an integral part of an overall shield which precludesthe problem of RF coupling (see FIGS. 5-7).

FIG. 40 illustrates the attenuation versus frequency response curvewhich is shown generically for the flat-through capacitor of FIG. 37. Ifit weren't for cross-coupling of RF energy, it would perform as an idealor nearly perfect capacitor would. However, because of thiscross-coupling, there is always going to be a certain frequency at whichthe attenuation starts to parasitically drop off as shown. This drop offis very undesirable in active implantable medical device (AIMD)applications in that there would be less protection against highfrequency EMI emitters such as cellular phones and the like. Thisparasitic drop off in attenuation due to cross-coupling is even a worseproblem in military and space applications where EMI filter attenuationrequirements of up to 10 or even 18 GHz, is important (implantablemedical applications don't generally require filtering much above 3 GHzdue to the effective reflection and absorption of human skin of RFenergy at frequencies above 3 GHz). Space and military circuits have tooperate in the presence of extremely high frequency emitters, such asGHz radars and the like. Accordingly, there is a need for a flat-throughtype of capacitor that eliminates the problems associated with thisparasitic attenuation degradation due to RF cross-coupling across (oroutside of around) the capacitor. In addition, there is also a need forflat-through capacitors that can handle much higher circuits throughtheir “through” electrodes. The present invention fulfills these needsand provides other related advantages.

SUMMARY OF THE INVENTION

A primary objective of the present invention is to provide a novelshielded three-terminal flat-through EMI/energy dissipating filter whichembodies one or more flat-through capacitors whose internal electrodesare high frequency shielded, are much thicker (compared to prior artMLCC flat-through thick film electrode technology) and higher in bothcross-sectional and surface area (robust and able to carry much higherthrough circuit currents), whose electrodes can be configured withintegral co-planar inductor elements, and can be optionally configuredto accept a variety of surface mounted electronic components (likeadditional discrete or embedded capacitors, inductors, diodes, RFIDchips, and the like). The higher surface area of the novel shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention maximizes the value of the flat-through capacitance. Thepresent invention resides in a shielded three-terminal flat-throughEMI/energy dissipating filter which comprises an active electrode platethrough which a circuit current passes between a first terminal and asecond terminal, and a plurality of shield plates substantiallyenveloping the active electrode plate, wherein the shield plates areconductively coupled to a grounded third terminal. Preferably, theplurality of shield plates include a first shield plate on a first sideof the active electrode plate, and a second shield plate on a secondside of the active electrode plate opposite the first shield plate. Theactive electrode plate is insulated from the shield plates by adielectric material such that the active electrode plate and the shieldplates cooperatively form a flat-through capacitor. A lead wiretypically extends through at least one of the shield plates innon-conductive relation. The lead wire is conductively coupled to theactive electrode plate to form the first terminal. A shielded fixturemay be provided through which the lead wire extends in non-conductiverelation. The fixture may comprise an hermetic seal for, for example, anactive implantable medical device (AIMD). The surface area of the activeelectrode plate is maximized to increase parasitic capacitance andminimize resistance to current flow.

In some embodiments, a plurality of active electrode plates are providedwhich each have a first shield plate on a first side thereof and asecond shield plate on a second side thereof opposite the first shieldplate. Each active electrode plate is insulated from its adjacent shieldplates by a dielectric material such that each active electrode plateand its adjacent shield plates cooperatively form a flat-throughcapacitor. The shield plates are conductively coupled to a commonground. A plurality of lead wires are provided which each extendsthrough at least one of the shield plates in non-conductive relation.Each lead wire is conductively coupled to a respective active electrodeplate to form the first terminal for said active electrode plate.

The shielded three-terminal flat-through EMI/energy dissipating filtermay further include an adjacent feedthrough capacitor through which thelead wire extends prior to conductively coupling to the active electrodeplate to form the first terminal.

A conductive pad may be conductively coupled to the active electrodeplate to form the second terminal. The conductive pad may comprise awire bond pad disposed on an exterior surface of a body of dielectricmaterial through which the active electrode plate extends.

The shielded three-terminal flat-through EMI/energy dissipating filtermay include a plurality of co-planar active electrode plates insulatedfrom the shield plates by a dielectric material such that each activeelectrode plate and the shield plates cooperatively form a flat-throughcapacitor. Moreover, at least one of the co-planar active electrodeplates may comprise an inductor. In several illustrated embodiments, aco-planar third shield plate extends between the co-planar activeelectrode plates.

In various embodiments, a lead wire or pin extends through at least oneof the shield plates in non-conductive relation, wherein the lead wireor pin conductively couples to the active electrode plate to form thesecond terminal. A monolithic chip capacitor (MLCC) may be conductivelycoupled between the active electrode plate and at least one of thegrounded shield plates. Further, a third shield plate may be disposedgenerally co-planarly with the active electrode plate, wherein the thirdshield plate is conductively coupled to the grounded third terminal. Thethird shield plate may substantially surround the active electrode plateand be disposed between the first and second shield plates.

The shielded three-terminal flat-through EMI/energy dissipating filtermay further be modified such that at least a portion of the activeelectrode plate comprises an inductor. The inductor may comprise aspiral circuit trace.

In various embodiments of the EMI/energy dissipating filter, at leastone via hole is provided for conductively coupling the shield plates toone another. The via holes may be disposed about the periphery of theactive electrode plate to enhance its shielding characteristics.

In various embodiments, the active electrode plate may be configured toform at least a component of an “L”, “pi” (π), “T”, “LL”, “5 element” oran “n” element passive electronic low pass filter. Moreover, the activeelectrode plate may be configured to form at least a component of a bandstop filter, a diode array, or an RFID chip. When used in connectionwith an active implantable medical device, the shielded three-terminalflat-through EMI/energy dissipating filter utilizes passive electronicdevice components which are optimized for use at MRI frequencies.

In some embodiments, the active electrode plate and the first and secondshield plates are disposed generally perpendicularly to a lead wireconductively coupled to the active electrode plate to form the firstterminal. In another embodiment, the active electrode plate and thefirst and second shield plates are disposed generally parallel to a leadwire conductively coupled to the active electrode plate to form thefirst terminal.

The active electrode plate and the shield plates are typically at leastpartially disposed within a hybrid flat-through substrate. This hybridflat-through substrate may include surface metallization forming thethird terminal. In many of the illustrated embodiments, the hybridflat-through substrate is disposed adjacent to a hermetic seal for animplantable medical device such that the surface metallization isconductively coupled to a housing for the implantable medical devicethrough a conductive ferrule of the hermetic seal.

The hybrid flat-through substrate may comprise a flex cable section, arigid section, or a composite of both types. The flex cable section maycomprise a polyimide, Kapton or acrylic material. The rigid section maycomprise a high dielectric constant ceramic, alumina, fiberglass or FR4material.

The rigid section of the hybrid substrate may include at least onepassive electronic component conductively coupled to the activeelectrode plate. The passive electronic component may comprise an RFIDchip, a capacitor, an inductor, a band stop filter, an L-C trap filter,a diode, or a diode array. The capacitor typically comprises amonolithic chip capacitor, and the inductor typically comprises amonolithic chip inductor or a toroidal inductor.

The second terminal of the active electrode plate may be conductivelycoupled to a circuit board for an electronic device, such as theinternal circuit board of an AIMD.

In another embodiment, the hybrid flat-through substrate comprises adielectric material with the active electrode plate embedded therein.The active electrode plate is conductively coupled to surfacemetallization for at least one via hole through the substrate. Theshield plates comprise surface metallization applied to exteriorsurfaces of the hybrid flat-through substrate, A conductive cap may beprovided which is configured to capture the hybrid flat-throughsubstrate and conductively couple the shield plates to a ground. Suchstructure may be utilized in connection with a hermetic seal for animplantable medical device. The hermetic seal would typically include aconductive ferrule to which the conductive cap is conductively attached,at least one lead wire extending through the ferrule in non-conductiverelation and conductively coupled to the surface metallization of thevia hole.

The shielded three-terminal flat-through EMI/energy dissipating filtermay be constructed such that all external components thereof comprisebiocompatible materials designed for direct body fluid exposure.Moreover, the aforementioned RFID chips may include a wake-up featurefor initializing AIMD RF telemetry circuits.

The aforementioned shielded three-terminal flat-through EMI/energydissipating filters may be incorporated into a passive component networkfor an implantable lead of an active implantable device (AIMD). Thepassive component network comprises at least one lead wire having alength extending between and to a proximal end and a tissue-stimulatingor biological-sensing electrode at a distal end, an energy dissipativesurface disposed adjacent to tissue or within the blood or lymph flow ofa patient at a point distant from the electrode, and a diversion circuitassociated with the lead wire, for selectively diverting high-frequencyenergy away from the electrode to said energy dissipative surface fordissipation of said high frequency energy as heat. The passive componentnetwork may include an impeding circuit associated with the diversioncircuit for raising the high frequency impedance of the lead wire. Theimpeding circuit is typically disposed between said diversion circuitand the distal end of said at least one lead wire, and typicallycomprises an inductor or a band stop filter.

The at least one lead wire may comprise a portion of a probe or acatheter. Moreover, the energy dissipative surface may comprise asheath, an insulative body, or a thermally conductive element. Moreover,the at least one lead wire may comprise at least a pair of lead wireseach having a length extending between and to a proximal end and atissue stimulating or biological-sensing electrode at a distal end. Thediversion circuit couples each of said lead wires to said energydissipative surface. The diversion circuit may further be coupledbetween the pair of lead wires.

The high frequency energy typically comprises an RF pulse frequency of amagnetic resonance scanner in a preferred embodiment. The high frequencyenergy may further comprise a range of selected RF pulsed frequencies.

The diversion circuit may comprise a low pass filter including at leastone of a C filter, and L filter, a T filter, a pi (π) filter, an LLfilter, a 5-element filter, or an “n” element filter. The diversioncircuit may further comprise at least one series resonant L-C trapfilter. Moreover, the impeding circuit may include a non-linear circuitelement. In this case, the non-linear circuit element may comprise adiode or a transient voltage suppressor. In various embodiments, thediversion circuit may comprise at least one series resonant L-C trapfilter, and wherein the impeding circuit comprises an inductor or a bandstop filter.

It will be appreciated that the basic point of novelty of thethree-terminal flat-through EMI/energy dissipating filter is that itcomprises an active electrode plate through which a circuit currentpasses between a first terminal and a second terminal, a first shieldplate on a first side of the active electrode plate, and second shieldplate on a second side of the active electrode plate opposite the firstshield plate, wherein the first and second shield plates areconductively coupled to a grounded third terminal. The effectivecapacitance area or overlapping surface area of the active electrodeplate and its surrounding grounded shield plates have been relativelymaximized in order to achieve a higher value of capacitance of thethree-terminal flat-through capacitor. The dielectric constant of theinsulating layers between the active electrode plate and the surroundingground shied plates have also been substantially raised in order toachieve a higher capacitance value for the three-terminal flat-throughcapacitor. Preferably, the dielectric thickness separating the activeelectrode plate and the surrounding ground shield plate is relativelyminimized in order to achieve a higher capacitance value. A number ofredundant parallel layers of the active electrode plate and surroundinggrounded shield plates are provided to increase the total capacitancevalue of the three-terminal flat-through capacitor.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a wire formed diagram of a generic human body showing a numberof implanted medical devices.

FIG. 2 is a fragmented perspective view of a prior art unipolardiscoidal feedthrough capacitor.

FIG. 3 is a sectional view of the feedthrough capacitor of FIG. 2 shownmounted to a hermetic seal of an active implantable medical device(AIMD).

FIG. 4 is a schematic diagram showing the feedthrough capacitor shown inFIGS. 2 and 3.

FIG. 5 is a perspective view of a quadpolar feedthrough capacitor.

FIG. 6 is sectional view taken along the line 6-6 of FIG. 5.

FIG. 7 is an electrical schematic diagram of the quadpolar feedthroughcapacitor of FIGS. 5 and 6.

FIG. 8 is an exploded electrode view showing the inner and outerdiameter electrodes of the unipolar feedthrough capacitor of FIGS. 2 and3.

FIG. 9 is an exploded view of the interior electrodes of the quadpolarfeedthrough capacitor show in FIG. 5.

FIG. 10 is a perspective view of a quadpolar feedthrough capacitormounted on top of a hermetic seal.

FIG. 11 is a sectional view taken generally along the line 11-11 of FIG.10.

FIG. 12 is an electrical schematic diagram of the quadpolar hermeticfeedthrough terminal shown in FIG. 10.

FIG. 13 is a perspective view of a monolithic ceramic capacitor (MLCC).

FIG. 14 is a sectional view taken generally along the line 14-14 of FIG.13.

FIG. 15 is an electrical schematic diagram of an ideal MLCC capacitor asillustrated in FIG. 13.

FIG. 16 is a more realistic electrical schematic diagram of the MLCCstructure of FIG. 13.

FIG. 17 is a chart giving the formula for resonance frequency.

FIG. 18 is a graph showing filter attenuation versus frequency.

FIG. 19 is a perspective view of a unipolar terminal having threedifferent size MLCC capacitors connected to the feedthrough pin.

FIG. 20 is an electrical schematic diagram of the structure shown inFIG. 19.

FIG. 21 is a graph showing the attenuation response for the three chipcapacitor unipolar hermetic terminal shown in FIG. 19.

FIG. 22 illustrates a different method of mounting the MLCC capacitorssuch as those shown in FIG. 19.

FIG. 23 illustrates a more desirable way to mount the capacitor of FIG.22.

FIG. 24 shows yet another way of mounting the MLCC capacitor of FIGS. 22and 23.

FIG. 25 is an electrical schematic diagram showing an equivalent circuitmodel for the MLCC chip capacitor.

FIG. 26 is a perspective and schematic view of a prior art MLCCtransient suppressant diode.

FIG. 27 is an electrical schematic diagram of the diode of FIG. 26.

FIG. 28 is a perspective and schematic diagram of a prior art chipinductor.

FIG. 29 is an electrical schematic diagram of the inductor chip of FIG.28.

FIG. 30 is a perspective view of an MLCC capacitor having an inductorcircuit trace deposited thereon.

FIG. 31 is an exploded perspective view of a structure similar to FIG.30 showing another way to deposit the inductor shape onto a separatesubstrate.

FIG. 32 is a perspective view of a composite monolithic ceramiccapacitor-parallel resonant tank (MLCC-T) or bandstop filter.

FIG. 33 is an exploded perspective view of the various layers of theMLCC-T tank filter of FIG. 32.

FIG. 34 is an electrical schematic diagram of the MLCC-T tank orbandstop filte r of FIGS. 32 and 33.

FIG. 35 is a sectional view of one pole of a quadpolar feedthroughcapacitor embodying an MLCC-T filter.

FIG. 36 is an electrical schematic diagram of the quadpolar devicepartially shown in FIG. 35.

FIG. 37 is a perspective view of a prior art flat-through capacitor.

FIG. 38 is a diagram showing the internal electrode array of theflat-through capacitor of FIG. 37.

FIG. 39 is an electrical schematic diagram of the prior art flat-throughcapacitor of FIGS. 37 and 38.

FIG. 40 illustrates the attenuation versus frequency response curve ofthe typical flat-through capacitor of FIGS. 37 and 38.

FIG. 41 is a perspective view of a quadpolar EMI filter hermetic sealsimilar to that shown in FIG. 10, but embodying a shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention.

FIG. 42 is a sectional view taken generally along the line 42-42 of FIG.41.

FIG. 43 is a sectional view taken generally along the line 43-43 of FIG.41.

FIG. 44 is a sectional view taken generally along the line 44-44 of FIG.41.

FIG. 45 is a sectional view taken generally along the line 45-45 of FIG.41.

FIG. 46 is a sectional view taken generally along the line 46-46 of FIG.41.

FIG. 47 is an exploded perspective view of the plates forming theflat-through EMI/energy dissipating filter of FIGS. 41-46.

FIG. 48 is a sectional view taken generally along the line 48-48 of FIG.41.

FIG. 49 is an electrical schematic drawing of the flat-throughEMI/energy dissipating filter of FIG. 41.

FIG. 50 is a sectional view similar to FIGS. 43 and 44 illustratingincorporation of stacked layers L₁ and L₂ into a single co-planar layer.

FIG. 51 is a sectional view similar to FIGS. 42-46, showing modificationof the active electrode plates for connection to a via hole.

FIG. 52 is a fragmented perspective view illustrating a lead wireextending into one of the via holes of FIG. 51.

FIG. 53 is a view similar to FIG. 52, showing an alternative bond pad inplace of the wire.

FIG. 54 is a perspective view of a unipolar hermetic seal similar tothat shown in FIG. 3, except that it is inverted with the feedthroughcapacitor replaced with a shielded three-terminal flat-throughEMI/energy dissipating filter of the present invention.

FIG. 55 is a fragmented view of the area indicated by line 55-55 in FIG.54, illustrating an alternative way of attaching a lead wire.

FIG. 56 is a sectional view taken generally along the line 56-56 of FIG.54.

FIG. 57 is a fragmented sectional view showing an alternative connectionmethodology wherein a via hole is filled and then attached to a solderbump.

FIG. 58 is an exploded perspective view of various components formingthe structure of FIGS. 54 and 56.

FIG. 59 is an electrical schematic for the structure of FIGS. 54, 56 and58.

GM-ACL-0676

FIG. 60 is a perspective view showing modification of an activeelectrode plate layer shown in FIG. 58.

FIG. 61 is a view similar to FIG. 60, wherein the active electrode platehas been modified by adding a spiral inductor element.

FIG. 62 is an electrical schematic for the inductor-capacitor filterformed by the substrate of FIG. 61.

FIG. 63 is an exploded perspective view of a quadpolar filter assemblyincorporating a shielded three-terminal flat-through EMI/energydissipating filter in accordance with the present invention.

FIG. 64 is a top plan view showing a modification of the grounded shieldplates of FIG. 63.

FIG. 65 is a view similar to FIG. 64 of the grounded shield plates,showing additional modifications.

FIG. 66 is similar to FIGS. 64 and 65, showing an alternativeconfiguration of the grounded shield plates.

FIG. 67 is a perspective view of an alternative arrangement of theactive electrode plate substrate of FIG. 63.

FIG. 68 is a graph illustrating attenuation versus frequency comparingthe performance of the shielded three-terminal flat-through EMI/energydissipating filter of FIG. 63 with other technologies.

FIG. 69 is an exploded isometric view that is similar to FIG. 63 whereinthe active electrodes have been modified to include inductors.

FIG. 70 is an exploded view very similar to FIGS. 63 and 69 except thatedge shields and optional separating shields have been placed to preventEMI radiation from the active electrode plates or optionally betweenco-planar electrode plates.

FIG. 71 is an exploded perspective view of an alternative form of theshielded three-terminal flat-through EMI/energy dissipating filtersimilar to FIG. 63.

FIG. 72 is an enlarged view of a round Wheeler spiral shown forming aportion of an active electrode plate in FIG. 69.

FIG. 73 is similar to FIG. 72, showing a square Wheeler spiral such asthose shown forming portions of the active electrode plates in FIGS. 69,70 and 71.

FIG. 74 illustrates several typical inductor meander shapes.

FIG. 75 illustrates the attenuation curves for various types of low-passfilters.

FIG. 76 is a family of filter attenuation curves similar to that shownin FIG. 68.

FIG. 77 is a perspective view of a bipolar hermetically sealed filterembodying the shielded three-terminal flat-through EMI/energydissipating filter present invention.

FIG. 78 is an exploded perspective view of the internal layers of theshielded three-terminal flat-through EMI/energy dissipating filter ofFIG. 77.

FIG. 79 is an exploded perspective view of an alternative embodimentembodying the shielded three-terminal flat-through EMI/energydissipating filter of the present invention.

FIG. 80 is a partially fragmented view of the assembled section of FIG.79 taken along the line 80-80 of FIG. 79.

FIG. 81 is an electrical schematic diagram of the quadpolar shieldedthree-terminal flat-through EMI/energy dissipating filter shown in FIGS.79 and 80.

FIG. 82 is an exploded perspective view of an inline hybrid substrateembodying the shielded three-terminal flat-through EMI/energydissipating filter of the present invention.

FIG. 83 is an electrical schematic diagram of the structure shown inFIG. 82.

FIG. 84 is an exploded perspective view of another form of a shieldedthree-terminal flat-through EMI/energy dissipating filter embodying thepresent invention.

FIG. 85 is similar to FIG. 84 except that the diode array has beenreplaced with an RFID chip.

FIG. 86 is similar to FIG. 84, wherein toroidal inductors have been usedto replace a series of surface mount chip inductors.

FIG. 87 is a view similar to FIG. 84, illustrating the flexibility of aportion of a hybrid substrate.

FIG. 88 is an internal diagrammatic view of the novel hybrid substrateof FIG. 84.

FIG. 89 is an electrical schematic diagram of the novel hybrid substrateof FIG. 84.

FIG. 90 is the same as one of the active circuits of FIG. 89 wherein the“T” circuit filter has been replaced with a IT circuit filter.

FIG. 91 is similar to FIG. 84, with the addition of a prior artquadpolar feedthrough capacitor.

FIG. 92 is a plan view of the reverse side of the flexible portion ofthe hybrid substrate of FIGS. 84 and 88.

FIG. 93 is a sectional view taken generally along the line 93-93 of FIG.92.

FIGS. 94-97 are fragmented sectional views taken generally of the areaindicated by the line 94, 95, 96 and 97 in FIG. 93, showing alternativemethods of making an electrical connection.

FIG. 98 is a plan view similar to FIG. 92 showing a modified version offlex cable assembly with four via holes.

FIG. 99 is a cross-sectional view of the area indicated by line 99-99 inFIG. 93, showing type of yet another embodiment illustrating attachmentof the substrate over a terminal pin utilizing a weld ring or a brazering.

FIG. 100 is a view similar to FIG. 99 illustrating yet anothermethodology of attachment.

FIG. 101 is an isometric cross-section of a novel attachment cap used toconnect the shielded three-terminal flat-through EMI/energy dissipatingfilter to various types of hermetic or non-hermetic seals.

FIG. 102 is a cross-sectional view of a prior art hermetic sealembodying the novel cap from FIG. 101.

FIG. 103 is a schematic view illustrating a methodology of having acircuit trace or a portion of an electrode plate dodge around a viahole.

FIG. 104 is a schematic illustration of an alternative embodiment toFIG. 84.

FIG. 105 is similar to FIG. 104, except that it illustrates themethodology of breaking up flex cable section of the hybrid substrateinto flexible sections.

FIG. 106 is an exploded perspective view of an in-line octapolarhermetic terminal with a shielded three-terminal flat-through EMI/energydissipating filter hybrid flat-through substrate embodying the presentinvention.

FIG. 107 is a flow chart illustrating a manufacturing productionprocess.

FIG. 108 is an exploded perspective view of a typical sixteen leadhermetic seal utilizing a novel hybrid shielded three-terminalflat-through EMI/energy dissipating filter embodying the presentinvention.

FIG. 109 is an electrical schematic diagram of the structure of FIG.108.

FIG. 110 is a perspective view of a five pin terminal.

FIG. 111 is a perspective view of the five pin terminal of FIG. 110 towhich a shielded three-terminal flat-through EMI/energy dissipatingfilter of the present invention is mounted.

FIG. 112 is a perspective view similar to FIG. 111, showing analternative embodiment wherein reversed geometry MLCC's are utilized toprovide high frequency attenuation.

FIG. 113 is a flow chart illustrating an exemplary manufacturing processof the electronic components of the present invention.

FIG. 114 is an illustration of an exemplary AIMD showing the use ofvariable impedance elements in connection with a lead wire within thehousing of the AIMD.

FIG. 115 is a schematic illustration of the structure shown in FIG. 114,showing use of variable impedance elements on leads that ingress andegress the AIMD.

FIG. 116 is a schematic illustration showing that a variable impedanceelement can be a capacitor element.

FIG. 117 is a schematic illustration similar to FIG. 116, showing thatthe variable impedance element can be a feedthrough capacitor element.

FIG. 118 is a schematic illustration similar to FIGS. 116 and 117,showing that the variable impedance element can be an L-C trap filter.

FIG. 119 is a schematic illustration similar to FIG. 118, showing use ofa capacitor element in parallel with the L-C trap filter.

FIG. 120 is similar to FIG. 115 with emphasis on the series variableimpedance element.

FIG. 121 illustrates that the variable impedance element can be aninductor.

FIG. 122 illustrates that the variable impedance element can be an L-Cbandstop filter.

FIG. 123 is an attenuation versus frequency chart showing impedancecharacteristics of various types of filters.

FIG. 124 is a schematic diagram of a series inductor-capacitor filtercommonly known in the industry as an L-C trap filter.

FIG. 125 is a chart giving the resonant frequency equation for an L-Cseries trap filter.

FIG. 126 illustrates the impedance Z in ohms versus frequency of theseries resonant L-C trap filter of FIG. 124.

FIG. 127 is similar to the chart similar to FIG. 126, illustrating theimpedance in ohms versus frequency of two discrete series resonant L-Ctrap filters.

FIG. 128 is an overall outline drawing showing a cardiac pacemaker withendocardial lead wires implanted into a human heart.

FIG. 129 is a cross-sectional view of a human head showing a deep brainstimulator electrode.

FIG. 130 is a schematic illustration of a unipolar lead system for anAIMD.

FIG. 131 is an illustration similar to FIG. 130, including an L-C trapfilter.

FIG. 132 is another illustration similar to FIG. 130, wherein thefrequency selective components comprise capacitive elements.

FIG. 133 is another illustration similar to FIGS. 130 and 132, whereinthe capacitance value C has been selected such that the capacitivereactance will be equal and opposite to the inductive reactance of theimplanted lead.

FIG. 134 illustrates prior art hermetic and non-hermetic connectors thatare typically used in the military, aerospace, medical,telecommunication and other industries.

FIGS. 135 and 136 illustrate a prior art sub D-type connector.

FIGS. 137 and 138 show prior art hermetic connectors.

FIG. 139 shows an exploded view of a prior art multi-pin connector and ashielded three-terminal flat-through EMI filter.

FIG. 140 is similar to FIG. 139 except that the shielded three-terminalflat-through EMI filter of the present invention has been attached.

FIG. 141 is an exploded view taken generally from section 141-141 ofFIG. 139 showing a surface mounted MLCC capacitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings for purposes of illustration, the presentinvention is concerned with shielded three-terminal flat-throughEMI/energy dissipating filters 190 which can be embodied in substratesor flex cable assemblies. The novel concept resides in designing anembedded flat-through capacitor wherein optional surface mounted passiveor active components can be attached while at the same time providing aninterconnection circuit. The novel shielded three-terminal flat-throughEMI/energy dissipating filters 190 embody a flat-through capacitor thathas similar characteristics to prior art feedthrough EMI filtercapacitors. The flat-through EMI/energy dissipating filter 190 of thepresent invention provides three-terminal capacitive filtering whilesimultaneously providing shielding of circuits and signals passingthrough the robust high current capability electrodes of theflat-through capacitor. The flat-through EMI/energy dissipating filter190 of the present invention functions in a very equivalent manner toprior art feedthrough capacitors in that: a) its internal ground platesact as a continuous part of the overall electromagnetic shield housingof the electronic device or module which physically blocks direct entryof high frequency RF energy through the hermetic seal or equivalentopening for lead wire ingress and egress in the otherwise completelyshielded housing (such RF energy, if it does penetrate inside theshielded housing can couple to and interfere with sensitive electroniccircuitry); and, b) like prior art feedthrough capacitors, theflat-through EMI/energy dissipating filter 190 of the present inventionvery effectively shunts undesired high frequency EMI signals off of thelead wire (electrodes) to the overall shield housing where such energyis dissipated in eddy currents resulting in a very small temperaturerise. Of course, unlike for prior art discoidal/feedthrough capacitors,in the present invention the circuit currents (for example pacemakerpacing pulses or ICD HV defibrillation high current shocks) must passthrough the internal electrodes of the embedded flat-through capacitor.By integrating flat-through technology into prior art circuit boards,substrates or flex cables, the flat-through electrodes can bemanufactured with much thicker electrodes (like copper sheet) whichgreatly increases their capability to safely carry relatively higherthrough circuit currents (like external or internal cardiacdefibrillation pulses).

As used herein and throughout this specification including its claims,the terms “connected electrically,” “connected,” “electricallyconnected,” “directly electrically connected,” “electrical connectionmaterial,” “wire connection,” “electrically speaking” and “conductivelycoupled” all mean the same thing and can be used interchangeably. All ofthese terms mean that there is an electrical connection between two (ormore) conductive structures. This often requires an electricalconnection material to affect an electrical connection between twoelectrically conductive structures or the two electrically conductivestructures may be immediately attached to each other. As used herein,these terms generally also include a mechanical connection with anelectrically conductive material. Importantly, “electrical connections”provide a low resistance and nearly zero impedance connection over abroad frequency range. In other words, “electrical connection”resistance (and its synonyms) provide a very low resistance connection(a few milliohms or tens of milliohms) at DC and also at high frequency.

In contrast, as used in this specification including its claims, theword “coupled,” “coupled to,” “couples,” or in some cases, “decoupled”means something entirely different. Unlike “electrical connection” or“directly electrically connected”, electrical coupling is through orbetween frequency variable circuit elements or structures which caninclude capacitive coupling, inductive coupling, mutual inductance,magnetic loop induction (transformer action) or antenna action byelectromagnetic waves and the like. Note: “conductively coupled” is anexception and it has the same meaning as “directly electricallyconnected” or “connected electrically” and is therefore listed in thepreceding paragraph.

FIG. 41 is a very similar to the quadpolar EMI filtered hermetic sealthat was illustrated in FIG. 10. In FIG. 41, in accordance with thepresent invention, the feedthrough capacitor element has been completelyeliminated, thus significantly reducing the cost of manufacture. Thefeedthrough capacitor 132 and its associated wire bond substrate 136that were described in FIG. 10 have been replaced by a novel shieldedthree-terminal flat-through EMI/energy dissipating filter 190. In FIG.41, wire bond pads 138, 138′, 138″, 138′″ and 140 are very similar tothe wire bond pads illustrated in FIG. 10. They are attached to arelatively higher K ceramic or suitable hybrid substrate 192. Novelparasitic flat-through capacitors of the present invention areintegrated into the substrate 192. This is better understood byreferring FIGS. 42 through 46.

FIG. 42 illustrates a grounded shield plate 194. In this case, thecenter pin 196 is grounded. That is, there is a web plate (not shown)underneath the substrate 192 wherein the ground pin 196 is electricallycoupled to the metallic ferrule 120 of the hermetic seal 112. It isimportant that this be a low inductance RF ground. In other words, theweb plate would be a high surface area plate with clearance holes onlyfor the pass through of lead wires 114, 114′, 114″ and 114′″. This RFgrounded web plate, could, for example, have its outer diameter laserwelded to the ferrule 120 of the hermetic terminal and its insidediameter hole welded or soldered to the grounded lead wire or pin 196.An alternative methodology of grounding the center pin 196 isillustrated with embedded ground plates within the hermetic seal asshown in FIG. 48. Referring to FIG. 48, one can see that there is ahermetic insulator 118 through which the lead wires pass innon-conductive relation to the metallic ferrule 120. Shown are groundplates 198 embedded in the insulative portion 118 of the hermetic seal112 which are attached by gold brazing to the center ground pin 196.Grounding this centered pin 196 using plates embedded in the insulator118 of the hermetic seal 112 has been described in U.S. Pat. No.7,199,995, the contents of which is incorporated herein by reference.Other methods of grounding pin 196 are further described in U.S. Pat.Nos. 5,905,627 and 6,529,103, the contents of which are alsoincorporated herein by reference.

FIGS. 43 through 46 illustrate the internal active electrode platelayouts 176, 176′, 176″ and 176′″. The overlap area which is otherwiseknown as the effective capacitance area (ECA) of each of these activeelectrode plates has been maximized in order to maximize theflat-through capacitance. Maximizing the thickness and the area of theactive electrode plates 176-176′″ also has an added benefit in thattheir overall resistance is lowered (and its current rating is greatlyincreased). This is important because circuit currents of the novelshielded three-terminal flat-through EMI/energy dissipating filter 190must pass through the respective electrode plates 176-176′″ in order toaccomplish the novel shielded flat-through capacitor characteristics.

As previously mentioned, one serious negative to prior art flat-throughcapacitors 174, such as shown in FIG. 37, is that it is not convenientlymountable in such a way that it becomes an integral part of an overallelectromagnetic shield. There is always a frequency at which undesirableRF coupling 188 across the device will occur. This usually does nothappen until 100 MHz or above. At very high frequencies, such as above 1GHz, this problem becomes quite serious. A second negative, as comparedto prior art discoidal feedthrough capacitors 110 and 132, where thecircuit current runs through a robust lead in a feedthrough hole, isthat the flat-through circuit currents must flow through the electrodesof the flat-through capacitor 174 itself. Limitations on electrodethickness and conductivity means that prior art flat-through capacitors174 have relatively high series resistance and can only be rated to afew milliamps, or at best, a few amps. However, a patient's pacemakerlead undergoing external (AED) defibrillation or an implantabledefibrillator must deliver a high voltage pulse of over 20-amps. Thenovel shielded three-terminal flat-through EMI/energy dissipating filter190 of the present invention overcomes both of the foregoing negativesassociated with prior art flat-through capacitors by incorporatinggrounded shield plates 194 surrounding on at least the top and bottomsides a novel high surface area and relatively thick flat-through activeelectrode plate 176 through which circuits of up to 30-amps or greatercan pass. As will be seen in subsequent drawings, the novel high surfacearea electrodes 176 of the shielded three-terminal flat-throughEMI/energy dissipating filter 190 can optionally include inductorsections which not only desirably add series inductance to the filterbut also increase the flat-through capacitance by increasing theeffective capacitance area (ECA).

Overall internal construction of the novel hybrid substrate 192 is bestunderstood by referring to the exploded view shown in FIG. 47. One cansee that each one of the flat-through active electrodes 176 through 176¹″ are sandwiched between a plurality of grounded shield plates 194,194′, 194″, 194′″, 194′″ and 194′″ as shown. The resulting high ECA hasthe effect of creating a very high value of flat-through capacitance forEMI filtering (typically several tens or hundreds of picofarads). Incontrast, the narrow (low surface area) circuit trace-type flat-throughdesigns taught by U.S. Pat. Nos. 5,683,435 and 6,473,314 are noteffective capacitor electrodes. This results in a flat-throughcapacitance that is nearly zero (only a stray picofarad which offers noeffective EMI filter attenuation by itself). In addition, by creatingthe flat-through capacitance between overlapping grounded shield plates194, the problem that was previously described in connection with theprior art structure of FIG. 37 has been eliminated. In FIG. 37, it wasshown that for a typical prior art flat-through capacitor, there is afrequency at which coupling 188 will occur. This is where the RF signalcan, through stray capacitance, antenna action or mutual inductance,avoid passing through electrode plate 175 and instead be coupleddirectly across the circuit traces or couple to adjacent circuit traces.This is best understood as previously described in FIG. 40 as thedegradation in attenuation due to cross-coupling. By shielding the highsurface area electrodes 176 of the novel shielded three-terminalflat-through EMI/energy dissipating filter 190 of the present inventionwith RF grounded shield plates 194 on both sides (and optionallyco-planar sides as well), this stray coupling problem and associatedhigh frequency attenuation degradation has been completely eliminated.Again, referring to FIG. 37, one can see that there is really no shieldbarrier from end-to-end of a prior art flat-through capacitor 174. Atsome frequency, for example around 100 MHz to 1 GHz, EMI or RF willundesirably cross-couple across the prior art flat-through capacitor 174or, potentially worse yet, couple to adjacent circuits.

Referring back to the novel construction as illustrated in FIGS. 41through 48, the flat-through capacitance is very well shielded. In thiscase, the flat-through capacitance will act as an ideal capacitor andwill be free of resonances and parasitic RF coupling degradation. InFIG. 48, one can see an optional external metallization 108 that isconnected to the interior grounded shield electrode plates 194. This isuseful to help prevent edge re-radiation of high frequency RF energywhich could couple to sensitive electronic circuits inside the overallshielded housing of the electronic device. In a preferred embodiment,the external metallization 108 would be directly electrically connectedto gold braze 124 (in this case, the diameter of the ferrule 120 wouldneed to be enlarged). Accordingly, the RF grounding and impedance wouldbe lowered between the ferrule 120 and the outer metallization 108 ofthe shielded three-terminal flat-through EMI/energy dissipating filter190. In this case, it will be obvious that the center ground pin 196could be eliminated and the internal ground electrodes 198 within thehermetic insulator 118 could also be eliminated. In other words, thegrounding of the shield electrode plates 194 could be accomplishedeither by the center pin 196 as shown in FIG. 48, or be done around theoutside perimeter or circumference with an attachment between theexternal metallization 108 and for example, gold braze 124. Addingmetallization 108 means that the embedded active flat-through electrodeplates 176 are RF shielded by top and bottom plates 194 and on theirco-planar edges by shield 108. This means that the active electrodeplates 176 are completely shielded such that RF re-radiation or crosscoupling cannot occur

Referring once again to FIG. 48, there is an insulative washer 200 whichis disposed between the shielded three-terminal flat-through EMI/energydissipating filter 190 and the hermetic insulator body 118. This is tomake sure that the electrical connection materials 128 cannot migrateunderneath the hybrid substrate 192 and cause shorting between adjacentpins. For example, if electrical conductive material 128 were to migratebetween pins 114″ and 114′″ this could short out the output of a cardiacpacemaker. Insulating layer 200, in a preferred embodiment is also anadhesive. This is desirable during manufacturing such that the shieldedthree-terminal flat-through EMI/energy dissipating filter 190 is firmlyaffixed to the hermetic seal 112. This makes the subsequent electricalattachment operations by soldering, centrifuging of thermally conductivepolyamides or epoxies or the like, more convenient.

Referring once again to FIG. 48, the body fluid side is shown on thebottom side of hermetic insulator 118. It is typical that electroniccircuits for AIMDs be inside the hermetic and electromagneticallyshielded housing. However, the present invention is not limited to onlyplacing the shielded three-terminal flat-through EMI/energy dissipatingfilter 190 on the inside of the housing of the AIMD. If one were toconstruct the shielded three-terminal flat-through EMI/energydissipating filter 190 of entirely biocompatible materials, there is noreason that it could not be disposed on the body fluid side. Referenceis made to U.S. Pat. No. 7,113,387 the contents of which are herebyincorporated herein, which describes EMI filter capacitors designed fordirect body fluid exposure. For example, active flat-through electrodesand their corresponding electrode shield plates could all be disposedwithin a non-lead containing high dielectric material and withconnections and electrodes and shield plates made of biocompatiblematerials such as pure platinum, gold, niobium, tantalum, titanium orthe like. In other words, the structure of FIG. 48 could be constructedsuch that it would be adapted for direct body fluid exposure.

FIG. 49 is a schematic drawing of the novel shielded three-terminalflat-through EMI/energy dissipating filter 190 of FIG. 41. Shields 194through 194′ illustrate the fact that the high surface area activeelectrode plates 176 are surrounded at least on top and bottom bygrounded shield electrode plates 194 that form the flat-througheffective capacitance overlap area and at the same time preventundesirable RF coupling across the flat-through capacitive filter. Thefeedthrough capacitances C₁, C₂, C₃ and C₄ have been formed by theoverlap area (ECA) between each of the active electrodes 176 and thecorresponding shield plates 194 that surround the active electrodes onboth top and bottom. For example, referring back to FIG. 47, one can seethat active electrode plate 176-176′″ have been surrounded on top andbottom by grounded shield plates 194-194′. The grounded shield plates194″ can be deposited by metal plating, thick film deposition(silk-screening), discrete metal sheets or similar processes on to adielectric layer which has a specific dielectric thickness d. It is wellknown to capacitor designers that the formula for the total flat-throughcapacitance is given by the formula C=kA(η−1)/d. In this formula, k isthe permittivity or dielectric constant of the insulative dielectricmaterial itself; A is the effective capacitance area in in.sup.2 ormm.sup.2 (ECA) determined by the overlap of the grounded shield plates194 and 194′ and, for example, the active electrode 176; n is the numberof total electrode areas; and, d is the dielectric thickness. Referringto FIG. 47, we can add insulative dielectric cover sheets (not shown)which can be the same or different insulating and/or dielectric materialthat forms the dielectric layer on each of the electrode layers (this isto add additional electrical and mechanical protection). It will beobvious to those skilled in the art of designing capacitors that blankcover sheets (as many as needed) could also be inserted between theactive electrode layers 176 and the associated or surrounding groundedshield plate layers 194. This would cause the dielectric thickness d tobecome greater which would have two effects. The first effect would beto increase the dielectric thickness and therefore the voltage rating ofthe flat-through capacitor. Thin dielectric layers tend to break down atrelatively lower voltages. Therefore, for a high voltage application,such as that of an implantable cardioverter defibrillator (ICD), onewould want a dielectric thickness that would be relatively greater thansay, for example, a low voltage pacemaker. When one examines theequation for capacitance, the dielectric thickness d appears in thedenominator. So as one increases the dielectric thickness then the totalflat-through capacitance would drop. Accordingly, the first decision adesigner makes is what is the required dielectric thickness for thevoltage rating of the application and then adjust the ECA such that thedesired flat-through capacitance is achieved. In some cases, not enoughflat-through capacitance will be achieved to adequately filter allfrequencies. As will be described in connection with subsequentdrawings, it will be shown how to add, by surface mounting or embeddingor thick film deposition, commercially available discrete capacitors,inductors, diodes and other components to enhance its overallperformance of the present invention, and in particular, the lowfrequency (LF) performance of the novel shielded three-terminalflat-through EMI/energy dissipating filter 190.

FIG. 50 illustrates a way to produce the novel hybrid EMI filtersubstrate 192 of FIG. 41 with less layers and a correspondingly loweroverall substrate thickness. This is accomplished by incorporating two(or more) active electrodes 176 and 176′ onto a single co-planar layer.Putting multiple active electrode plates on co-planar layers has thedesired effect of making the shielded three-terminal flat-throughEMI/energy dissipating filter 190 thinner, easier to manufacture andless expensive. However, this has the undesirable effect of reducing theeffective capacitance area (ECA) for each active electrode plate 176.However, when high K materials are used, the effective capacitance areais so large that this is really not a detriment. Also, subsequentdrawings will show methods of adding co-planar inductor-electrodes toboost the filter attenuation. It will be obvious to those skilled in theart that in a similar manner, active electrodes 176″ and 176′″ couldalso be incorporated into a single combined layer. The novel shieldedthree-terminal flat-through EMI/energy dissipating filter 190, andparticularly its hybrid substrate 192, can be constructed of prior artflex circuit techniques (like polyimide flex circuits), multilayer rigidsubstrates (like alumina or FR4 board), thick film deposition onto asubstrate or carrier, or the like. For each of these manufacturingtechniques, there is a practical limit to the number of layers that canbe built up. This limitation has to do with limitations of the inherentmanufacturing process. For example, when one builds up a sufficientnumber of layers (more than 8 to 10), then a flex circuit starts tobecome fairly rigid. In fact, it's common in flex cable design that aportion of the flex cable be built up and become a portion known as“rigid-flex.” The present invention allows the shielded three-terminalflat-through EMI/energy dissipating filter technology to be used incompletely flexible substrates, hybrid substrate designs that have botha flexible and a rigid layer, or in a completely rigid board.

Referring back to FIG. 41, one can see that there are wire bond pads 138through 140 as shown. The addition of wire bond pads adds a circuitconnection convenience and an additional expense. In comparison, FIG.51, shows that, for example, the active electrode plate 176 shown inFIG. 43 could be modified such that it was connected to a via hole 202.This via hole 202 provides for a convenient connection of either a leadwire 204, as shown in FIG. 52, or a round (or rectangular, square orother not shown) wire bond pad 206 as illustrated in FIG. 53.

FIG. 54 is an isometric drawing of a unipolar pacemaker hermetic seal112 that is similar to that shown in FIG. 3 except that the feedthroughcapacitor has been replaced with a shielded three-terminal flat-throughEMI/energy dissipating filter 190 of the present invention shown mountedon top of the insulator 118 and gold braze 124. The hybrid substrate 192of the shielded three-terminal flat-through EMI/energy dissipatingfilter 190 can be manufactured from any number of the techniquespreviously described herein. The body of the hybrid substrate 192 couldbe a conventional substrate consisting of high dielectric constantceramic, alumina, ceramic, fiberglass, FR4 or any other rigid type ofmulti-layer board technology. In addition, it could be made of a numberof flexible or flex cable variances. These could include flex cablesthat are laminated together based on polyimide, Kapton and acrylicconstruction. Another embodiment would be polyimide flex cables with allpolyimide connections which are laminated together at high temperature.All of these types of boards and/or substrates and/or flex cables areknown in the art. What is described herein is a very novel adaptation ofthose boards and substrates to flat-through filter technology.Hereinafter, the novel substrates incorporating various forms of novelshielded flat-through EMI filter technologies will be referred to as thehybrid substrates 192.

In FIG. 54, one can see that there is a metalized area 208 on the hybridsubstrate 192. This wrap-around metalized area 208 makes connection tointernal ground shield plates 194 and 194′ embedded within the hybridsubstrate 192 as shown in FIG. 56. One can see in FIG. 54 a plurality ofelectrical connections 210, 210′ and 210′″ as shown (the equivalentelectrical connections 210″ and 210″″ on the opposite side of substrate192 are not shown). These electrical connections connect to gold braze124 that is part of the hermetic seal and provides an “oxide-free” RFground multi-point connection. This is better understood by referring toFIG. 56 which is taken from section 56-56 of FIG. 54. The importance ofconnecting to a gold braze instead of connecting directly to thetitanium ferrule 120 can be better understood by referring to U.S. Pat.Nos. 6,765,779 and 6,765,780 the contents of which are incorporatedherein. From FIG. 56, one can see that there is a prior art hermeticseal 112 which includes a metal ferrule 120 which is typically oftitanium or the like. There is a flange area 212 shown which isconvenient for laser welding to the titanium housing of an AIMD, such asa cardiac pacemaker or the like. There is a hermetic insulator 118 whichcan be of alumina, ceramic materials, glass or equivalent. In thisparticular embodiment, there is a gold braze 124 which forms amechanical and hermetic seal between the insulator 118 and the ferrule120. A gold braze 122 makes a similar mechanical and hermetic sealbetween the lead wire 114 and the insulator 118. In this example, thebody fluid side would be towards the bottom of the cross-sectionalillustration of FIG. 56. An electrical connection is made between leadwire 114 and the metalized via hole 202 which is part of the novelhybrid substrate 192. The via hole 202 makes electrical connection tointernal active electrode (otherwise known as the flat-throughelectrode) plate 176 as shown, which in turn is connected to via hole202′. The grounded electrode shield plates 194 and 194′ are connected tothe outside metallization surface 208 of the hybrid substrate 192. Inturn, this metallization 208 is electrically connected via material 210to the gold braze 124 of the hermetic seal 112. As previously stated,this direct connection to gold makes a reliable oxide free low impedanceconnection, the importance of which is described thoroughly in U.S. Pat.Nos. 6,765,779 and 6,765,780. One can also see that by wrappingmetallization surface 208 around the sides of the hybrid substrate 192,one prevents any chance that EMI being conducted on active electrode 176could radiate or cross-couple into the interior of the AIMD. By keepingthe EMI “bottled up” between the grounded shield plates 194 and 194′,one forms a nearly complete faraday cage shield which is the idealsolution. Due to the thin geometry, substrate edge re-radiation of RFenergy is a very minor concern which, if the dielectric thicknessbetween layers 176 and 194, 194′ becomes large, can be solved byco-planar edge shields which will be described in connection with FIG.60. This novel method of shield containment is applicable to any of theembodiments described herein.

Referring once again to FIG. 54, one can see that a prior art monolithicceramic chip capacitor (MLCC) 142 has been electrically connected tolands which are in turn connected to via holes 202′ and 202″. This isbetter understood by referring to the exploded view of FIG. 54 shown inFIG. 58. One can see that via hole 202′ is connected to the activecircuit electrode 176. The other side of the MLCC capacitor 142 isconnected by via hole 202″ to both of the grounded shield electrodeplates 194 and 194′. It is important that a very low impedanceconnection has been made to both sides of the MLCC capacitor 142. Inthis embodiment, any type of chip capacitor could be used. That is,monolithic ceramic, stacked film, tantalum, electrolytic or the like. Itwill also be obvious to those skilled in the art that the ground (left)side of MLCC capacitor 142 need not be connected to RF ground by way ofthe via 202″ as shown. Instead, an enlarged land on the left side of theMLCC 142 could be RF grounded directly to the external wrap-aroundmetallization surfaces 208.

In FIG. 54, one can see that there is a wire bond pad 138 which isaffixed to the hybrid substrate 192. This makes for a convenientmounting pad for attachment of lead wire 204. Lead wire 204 would berouted to the internal circuits of the general electronic device or anAIMD. Lead wire 204 can be affixed to wire bond pad 138 by thermal orultrasonic welding, soldering or the like. FIG. 55 shows an alternativearrangement wherein the wire bond pad 138 (which would typically be madeof Kovar) has been eliminated. In FIG. 55, there is a different type ofplated of metal deposited wire bond pad 139. In this case, no separateattachment of a Kovar block 138 is required as illustrated in FIG. 54.In this case, in FIG. 55, wire bond pad 139 can be an integral part ofan external circuit trace and deposited by plating, thick filmdeposition technique and the like.

Referring once again to FIG. 56, active electrode plate 176 issandwiched between the two grounded electrode shield plates 194 and194′. The prior art MLCC capacitor 142 is connected between via hole202′ (which is also connected to the active circuit plate 176) and viahole 202″ which is in electrically conductive relationship with both theground shields 194 and 194′. Electrically speaking, this means that theMLCC capacitor 142 connects from the active circuit plate 176 to ground.Accordingly, it acts as an electrical bypass low-pass filter element toprovide additional EMI filtering to complement the flat-throughcapacitance as previously described.

Referring once again to FIG. 56, one can see that there is an electricalconnection material 214 that is disposed between the lead wire 114 andthe via hole 202. This can be of a thermal setting conductive polymer,such as a conductive epoxy or a conductive polyimide or the like.Material 214 could also be of solder or braze, which is known in the artas solder bump construction or even ball grid array (BGA). It is shownin the reflowed position so it is not obvious that this started out as around ball. In order to provide electrical isolation between thismaterial 214 and the gold braze 124, one or more adhesive backedinsulative washers 200 are disposed between the hermetic seal 112 andthe hybrid substrate 192. Typically this washer 200 would be an adhesivebacked polyimide or the like to make sure that electrical conductivematerials such as 214 stay in place and could not short and/or migrateto areas where they were not desired (like a short to ground). Asdescribed in U.S. Pat. No. 7,327,553, the contents of which areincorporated herein by reference, a laminar leak detection path can beprovided between the washer 200 to facilitate helium leak testing of thehermetic seal.

There is a similar electrical connection material 210 disposed betweenmetallization surface 208 and gold braze 124. Material 210 is alsotypically a thermal setting conductive adhesive, solder, low temperaturebraze, laser weld, or the like. A wire bond pad 138 is shown connectedto the active electrode plate 176. At this point, any electrical noise(EMI) that was entering from the body fluid side on lead wire 114 hasbeen decoupled by the filtering action of the flat-through capacitancesshown in FIG. 56 as C_(P) and C_(P′) and the MLCC 142 working together.The flat-through capacitance is relatively lower in value than the MLCC142; however, it is very effective for attenuating high frequencies.Lower frequencies are attenuated by the higher capacitance value MLCCcapacitor 142. Wire bond pad 138 is convenient for connection of one ormore lead wires 204 to internal circuit components inside of the generalelectronic shielded module or an AIMD.

In FIG. 56 one can see that via hole 202 is connected to lead wire 114by means of an electrical conducting material 214 which can be solder, alow temperature braze, a thermal-setting conductive adhesive or thelike. An alternative methodology is shown in FIG. 57 wherein the viahole 202 is filled and then attached to a solder bump 216 as shown. Thesolder bump 216 makes contact to the metallization 106 of via hole 202.By raising the entire assembly to an elevated temperature, the solderbump 216 wets to the nail head lead 218 forming a reliable electricaland mechanical connection.

FIG. 58 is an exploded view of FIG. 54. A low impedance RF electricalconnection to the ground shield plates 194 and 194′ is very important.Accordingly, one can see that there are multiple electrical attachments210 to 210″″. This, of course, could be one long continuous connectionall around the ground metallization 208 to the gold braze 124. However,it is desirable to not block a helium leak path. The integrity of thesehermetic terminals is critical to preclude the entry of body fluid intothe AIMD.

Referring once again to FIG. 56, one can see that if there were a crack220 or other defect in the hermetic terminal insulator 118 or in thecorresponding gold braze 122 then body fluid (moisture) may be able toenter into the enclosed electronic housing or worse yet, the hermetichousing of an AIMD like a cardiac pacemaker. It is very common in theart to test these terminals using helium as a leak detection medium.However, a concern is that the installation of adjunct components, suchas the hybrid substrate 192 of the present invention, could temporarilyblock the flow of helium. Typically a helium leak test is performed in afew seconds. Therefore any adjunct sealant, such as a continuouscoverage of conductive thermal setting adhesive 210 or the like, couldslow down the flow of helium through such coverings. Accordingly, in thepreferred embodiment of the present invention, it is desirable to leaveopen gaps as shown in FIGS. 54 and 58 between areas of electricalattachment. In this way, if there are any defects 220 in the hermeticterminal insulator 118 or its associated gold brazes 122 and 124, thehelium will be free to pass and be detected by the leak test equipment.As taught by U.S. Pat. No. 6,566,978, the contents of which areincorporated herein by reference, it will be obvious to those skilled inthe art that strategically placed open via holes through the hybridsubstrate 192 could be provided in order to pass helium during hermeticseal testing.

Referring once again to FIG. 58, a novel aspect of the present inventionis that flat-through capacitance develops between the circuit activeelectrode plate 176 and the surrounding grounded shield electrode plates194 and 194′. This capacitance is shown as C_(P) and CP_(P′). Thecapacitance value of this flat-through capacitance is dependent upon thetypical capacitance equation, which is given by C=kA(η−1)/d. Where k isthe dielectric constant of the material. As previously mentioned, thenovel hybrid substrate 192 shown in FIG. 56 could be constructed of avariety of different materials. For example, the dielectric constant ofa polyimide material would be between 3 and 4 whereas an alumina ceramicmaterial could be as high as 9 to 11. Barium and strontium titanatedielectric bodies can have dielectric constants in excess of 5000. Inthe equation, A stands for the area, which is the effective capacitancearea (ECA). This is calculated by the sandwiched overlap between thearea of circuit active electrode plate 176 and the corresponding groundelectrode shield plates 194 and 194′. Ignoring fringe effects, asimplified way of calculating this area is simply the area of activeelectrode plate 176 that is bounded between the sandwiched groundedshields 194 and 194′. In the equation, n is the total number ofrepetitive electrode plates. In this case, there are three platesconsisting of 194, 176 and 194′. This gives us η−1 which yields twoparasitic flat-through capacitances C_(P) and C_(P′). The dielectricthickness d is simply the thickness of the dielectric material thatseparates 194 and 176; and 176 and 194′ as shown. The presence of theflat-through capacitances C_(P) and C_(P′) is extremely important to theoverall broadband EMI filtering performance of the present invention.This can be understood by referring to the schematic diagram of FIG. 59.In addition to the flat-through capacitances Cp, C_(P′) . . . C_(Pn),there is also parasitic inductance formed along the length of the activeelectrode plate 176. This is shown as L_(P), L_(P′), and L_(Pn). It willbe obvious to those skilled in the art that the higher the amount of theeffective capacitance area that overlaps between the active electrodeplate 176 and the adjoining ground shield plates 194 and 194′, thehigher the parasitic capacitance C_(P) will be. In this case, theparasitic inductance is very small and really does not aide infiltering. It will also be obvious to those skilled in the art that theparasitic inductance of the active electrode 176 will be proportional toboth its length and its width. In other words, the longer the activeelectrode 176 is, the greater its inductance L_(P) will be. The presenceof series inductance is very important as this will improve the overallhigh frequency performance of the shielded three-terminal flat-throughEMI/energy dissipating filter 190. There are ways of making this slightseries parasitic inductance much higher as will be described below.

Referring back to schematic FIG. 59, one can see that in a number oflocations there is a shield symbol 194-194′″ (sometimes shown as “Sh”).This is an indication that the entire assembly consisting of theflat-through capacitance C_(P) and the capacitance C contributed by theMLCC capacitor 142, in general, has its active electrode all contained(sandwiched between) within the shield plates 194. As previouslymentioned, this is very important so that undesirable electromagneticinterference at high frequency cannot bypass or jump across from thebody fluid side and thereby enter into the electronic device or AIMDhousing and possibly interfere with sensitive electronic circuits. Theimportance of filtering for AIMDs, such as cardiac pacemakers, has beendescribed by U.S. Pat. Nos. 4,424,551, 5,333,095 and 5,905,627 thecontents of which are incorporated herein. In this regard, the shieldedthree-terminal flat-through EMI/energy dissipating filter 190 of thepresent invention acts in equivalent way to prior art feedthroughcapacitors in that the shielded three-terminal flat-through EMI/energydissipating filter 190 is not only an effective filter and energydissipation element, it's ground electrode plates 194 act as aneffective part of the overall electromagnetic shield housing of the AIMDor other equivalent shielded electronic circuit.

Referring back to FIG. 58, one can see that in the presentconfiguration, the inductance, although quite small, is relativelymaximized due to the relatively long length of active electrode plate176 and the fact that it is relatively narrow. One will also notice thatthe flat-through (parasitic) capacitance is the sum of the parallelcombination of C_(P) and C_(P′), and is relatively maximized due to thelarge area of the active electrode 176 and the high ECA achieved by itsoverlap with the grounded shield plates 194 and 194′. One way to furtherincrease the total amount of flat-through (parasitic) capacitance wouldbe to increase the number of layers in FIG. 58. In a monolithicconstruction, repeating the number of redundant layers would increasethe capacitance by the η−1 term of the capacitance equation. Additionalways to increase the amount of flat-through capacitance would be tofurther increase the effective capacitance overlap area ECA, increasethe dielectric constant or decrease the dielectric thickness (d).

Prior art feedthrough capacitors, as illustrated in FIGS. 2 and 5 andshown in the assembly in FIG. 10, make for very low inductance broadbandlow-pass filters. This is why they have generally been the preferred EMIfilter at the point of lead wire ingress and egress for AIMDs and otherdevices. However, feedthrough capacitors are generally built in lowvolumes in the industry. Because of this, they tend to be relativelyhigh in price when compared to the much higher volumes MLCC capacitors.It is not unusual for a single feedthrough capacitor to cost severaldollars, wherein an MLCC capacitor can cost just a few cents. Inaddition, prior art feedthrough capacitors tend to be quite low incapacitance value (primarily in the range from 400 to 4000 picofarads).This means that prior art feedthrough capacitors make very effectivehigh frequency filters above 25 MHz, but off little attenuation at lowfrequencies (below 5 MHz). Feedthrough capacitors, in general, can be ahundreds of times more costly than equivalent value MLCC capacitors.However, referring back to FIG. 13, for the MLCC capacitor and its highfrequency performance curve, as illustrated in FIG. 18, this does notproduce a broadband low-pass filter. In general, MLCCs are marginal orinsufficient for attenuating high frequency emitters that AIMD patientscan be exposed to. This includes cellular telephones, RF identification(RFID), airport radars, microwave ovens and the like. As described inconnection with FIG. 37, one possible solution would be to useflat-through capacitor technology. However, the parasitic degradation ofattenuation due to cross-coupling as illustrated in FIG. 40 is a seriousproblem. Another problem associated with the prior art flat-throughcapacitor of FIG. 37 is that it is relatively costly. This is not justbecause it is produced in relatively low volumes. There are additionalcosts required for the additional flat-through terminations 222 and 222′as shown in FIG. 37. These added terminations are difficult to automateand add significant hand work and additional expense. By incorporatingthe flat-through capacitor electrode plate 176 as a distributiveparasitic element sandwiched between ground shield plates 194 and 194′,as illustrated in FIG. 58, a number of desirable goals are achieved.First of all, the problem of cross-coupling across the flat-throughcapacitor has been eliminated. This is because it is contained orsandwiched within an entirely shielded structure. Therefore, there is noway for high frequency EMI to couple across the novel shieldedthree-terminal flat-through EMI/energy dissipating filter 190 of thepresent invention. In addition, flex cables for circuit boards arealready commonly used in prior art electronic devices including AIMDs.In other words, by not adding any additional structures, one can embed aflat-through capacitance and then combine it with an MLCC capacitor 142(or additional components) as shown in FIG. 58. The MLCC capacitor 142is effective for low frequency attenuation and the parasiticflat-through capacitance C_(P) works to attenuate high frequencies. Theparasitic capacitance or flat-through capacitance works in parallel withthe capacitance of the discrete MLCC capacitor 142 which results in avery effective broadband low-pass filter from kilohertz (kHz)frequencies all the way to 10 gigahertz (GHz) or higher. This is allsummarized by the schematic diagram shown in FIG. 59. Shields194-194.sup.n are illustrative to indicate that the entire flat-throughfilter is sandwiched between RF shield plates in such a way that highfrequency EMI signals cannot re-radiate from the active electrodeplate(s) 176. This is a very important concept. Until the undesirableEMI energy is decoupled to ground, it cannot be left unshielded insidethe overall electromagnetically shielded housing of the electronicdevice or AIMD. If left unshielded, such high frequency noise couldcross-couple into sensitive AIMD sense circuits. For example, if acardiac pacemaker senses such high frequency noise as a heartbeat, thepacemaker could inhibit which could be life-threatening for apacemaker-dependent patient.

FIG. 60 illustrates an alternative active electrode layer to that whichwas previously described as 176 in FIG. 58. Referring to FIG. 60, onehas to imagine removing the exploded active electrode view layer 176 inFIG. 58 and replacing it with the active electrode 176′. The activeelectrode plate 176′ itself is not much different from that previouslyillustrated in FIG. 58 (its surface area is slightly smaller). What isdifferent is that a grounded or third shield trace 224 has beendeposited around the active electrode 176′ on the same co-planarsurface. The purpose of the surrounding grounded shield trace 224 on thesame plane as active electrode 176′ is to further aid in the coaxialshielding of the active electrode plate 176′. When one considers thatthe active electrode 176′ is already sandwiched between grounded shieldplates 194 and 194′, this means that it is now shielded top, bottom andon both sides. The addition of the optional edge shield 224 preventsedge radiation of high frequency from the shielded three-terminalflat-through EMI/energy dissipating filter 190.

The filter performance of the flat-through capacitor can be furtherimproved by additional low-pass circuit elements. Referring to FIG. 61,one can see that the active electrode plate 176″ has been modified byadding a Wheeler spiral inductor element 158. Wheeler spiral inductorsare well known in the prior art for a variety of other applications.Wheeler spiral design equations are also readily available. The spiralinductor circuit trace 158 adds substantial series inductance to theactive electrode plate 176″ and also increases the flat-throughcapacitance overlap area (ECA) as well. In FIG. 61, by also having awide active electrode plate area 176″, one also maximizes the parasiticflat-through capacitance as previously described. In other words, theincreased total effective overlap area (ECA) between the inductorcircuit trace of 158 and the active electrode plate 176″ as they aresandwiched between the two ground shield plates 194 and 194′ greatlyincreases the flat-through capacitance C_(P) and C_(P′). In the art ofEMI filter design, when one places an inductor in series with thecircuit along with a capacitance to ground, this is known as anL-section low-pass filter. The schematic for the L-section filter ofFIG. 61 is shown in FIG. 62.

Referring to FIG. 62, one can see the Wheeler inductor spiral 158 is inseries with the active electrode 176″ which has in parallel to groundboth the flat-through parasitic capacitance C_(P), and the MLCCcapacitor 142 to form an L-filter. Not shown in FIG. 62 is the fact thatthe parasitic capacitance C_(P) is really a distributive element andshould be shown throughout the circuit. Accordingly, FIG. 62 should beconsidered a relatively low frequency model wherein a high frequencymodel would be of a distributed transmission line.

FIG. 63 illustrates a quadpolar filtered feedthrough assembly inaccordance with the present invention. It is very similar inconstruction as previously described for the unipolar device of FIGS.54, 56 and 58. In FIG. 63, one can see that there are multiple groundelectrode shield plates 194, 194′ and 194″. The associated via holeswill be obvious to those skilled in the art.

Sandwiched between these ground electrode shield plates are activecircuit electrode layers 226 and 228. Flat-through electrode circuits176 and 176′ are contained on electrode circuit trace layer 226. Aspreviously described, parasitic capacitances or flat-throughcapacitances are formed due to the ECA overlap area on both sides. Thespacing of the ground shields 194 and 194′ is quite important in thatthey should not be spaced too far apart or high frequency RF leakagecould occur due to the electromagnetic interference signals re-radiatingfrom the flat-through electrode plates 176 and 176′ out through theoutside edge. This RF leakage was prevented in the unipolar design ofFIG. 54 by wrapping the metallization surface 208 around the outside,This can also be accomplished by stitching through a number ofconductive filled via holes 230 as shown in FIG. 64. FIG. 64 is amodification of the ground shields 194-194″ of FIG. 63. One can see thatthere are a plurality of these stitching vias 230 or grounding vias allaround the perimeter and even inside. The purpose of these stitchingvias 230 is to electrically connect the three (or n) ground shieldlayers 194-194″ together in a multi-point low inductance configuration.These stitching vias form another very important purpose in that theydecrease the effective length when one looks at the side view of thislaminated sandwiched structure. It is a common principle in waveguideengineering that the cutoff frequency of a waveguide is dependent uponits geometry. For rectangular waveguides, the length-to-width ratios arevery important. By shortening the length, one greatly increases thefrequency at which the waveguide could start to pass electromagneticsignals through it. Accordingly, by including many stitching vias 230,one is guaranteed that the sandwiched construction maintains RFshielding as to edge re-radiation integrity up into the 5 to 10 GHzregion. This is well above the effective filtering frequency requiredfor AIMDs. The upper frequency for AIMDs is defined by experts in theart as 3 GHz. The reason that attenuation above 3 GHz is not requiredfor AIMD EMI filters has to do with the reflection and absorption ofbody tissues at very short wavelengths. Accordingly, it is generallyaccepted by the implantable medical device EMC community thatelectromagnetic filters need to be very effective up to 3 GHz, but notbeyond. References for this is made to published ANSI/AAMI standardPC69.

Referring once again to FIG. 63, it will be obvious to those skilled inthe art that multiple layers n could be stacked up. The reason for thiswould be two fold. That is, to increase effective capacitance area (ECA)for the flat-through capacitances formed between the active electrodeplates 176.sup.n and the surrounding ground shields 194.sup.n and alsoto increase the current handling capability of the active circuitelectrode plates by putting additional redundant electrodes in parallel.This would tend to decrease the series resistance of said active circuitelectrodes and, at the same time, increase their current and powerhandling capabilities.

Referring once again to FIG. 64, another purpose for the multiple vias230 is to increase the mechanical integrity of a flexible hybridsubstrate 192. By having multiple vias 230 stitching through, it becomesmuch more unlikely that said structure could delaminate. Another way toaccomplish this is shown in FIG. 65, by the use of slot patterns 232.

In FIG. 65, there are multiple slots 232 as shown. These slots can beplaced in a number of areas. The slots 232 are generally not filled inthe same way that a via hole is filled. However, it does allow theadhesive binder layers to contact through the metalized electrodeshield. For example, in a typical polyimide flex cable arrangement,multiple layers of polyimide are laid up with an acrylic binder. In thisway, by providing for the slots 232, the acrylic binder can contact theunderlying substrate material 234.

Referring back to FIG. 65, in the present invention it is preferable toalign the slots 232 in the direction of active electrode circuit currentflow such that torturous paths are not created for current flow. Thisalso tends to maintain the inductive integrity of the ground plate. Byway of example, if the shielded three-terminal flat-through EMI/energydissipating filter 190 of the present invention were used at the pointof lead wire ingress of a cardiac pacemaker, then the active electrodesmust be low loss in order to conduct both the pacemaker pacing pulsesand also conduct the biologic sensing signals. In other words, a moderncardiac pacemaker actively detects and monitors the electrical activityof the heart. One purpose for low loss active electrodes is as an AIMDbattery saving purpose. Some patients are not pacemaker dependent,meaning that they only need to be paced at certain critical times whentheir heart rate drops too low. Therefore the pacemaker electroniccircuits constantly monitor the heart. When a pacing pulse is needed,the pacemaker activates and delivers the pacing pulse through implantedleads to the appropriate cardiac tissue. The stimulation pulse thenrestores the heart to its natural sinus rhythm. Accordingly, it is veryimportant that the active electrodes, such as those shown in layers 226and 228 of FIG. 63, be relatively low loss. That is, the resistivity ofthe active electrodes should not be so high that pacing pulses orsensing signals are significantly attenuated.

FIG. 66 illustrates a methodology of putting multiple holes 236 in themetalized electrode shield. These multiple holes 236 serve the samepurpose as the previously described slots 232 in FIG. 65.

FIG. 67 shows an alternative arrangement for the active electrode layer226 previously shown in FIG. 63. In FIG. 67, one could imagine that thislayer 226′ could replace layer 226 in FIG. 63.

FIG. 68 is a graph illustrating attenuation versus frequency comparingthe performance of the shielded three-terminal flat-through EMI/energydissipating filter 190 of FIG. 63 with a prior art feedthrough capacitorand a prior art MLCC. One can see significant differences in thecomparison of a conventional feedthrough capacitor with that of an MLCCcapacitor and the shielded three-terminal flat-through EMI/energydissipating filter of the present invention. In FIG. 68, the feedthroughcapacitor and the MLCC are of equal capacitance value. The capacitancevalue of the shielded three-terminal flat-through EMI/energy dissipatingfilter is significantly less. The feedthrough capacitor exhibits a smallself-resonant dip shown as SRF₁. Feedthrough capacitors are unique inthat after they go through this type of transmission line selfresonance, they continue to function as a very effective broadbandfilter. The opposite is true for a prior art MLCC capacitor. The MLCCcapacitor actually outperforms at its resonant frequency SRF othercapacitor technologies, however, at frequencies above its self-resonantfrequency SRF, it very rapidly becomes inductive at which point theattenuation decreases versus frequency. This is highly undesirable, ashigh frequency emitters, such as cell phones, would not be properlyattenuated. The flat-through capacitance in the present invention is aparasitic capacitance and it tends to be a relatively low capacitancevalue. That means that its effective 3 dB point (or point where itstarts to become an effective filter) is relatively high in frequency.In this case, the 3 dB point is approximately 1000 MHz. In accordancewith the design of FIG. 63, when one combines the MLCC capacitorresponse curve with the flat-through parasitic curves (these twocapacitances are added in parallel). FIG. 68, illustrates the compositeor added response attenuation curve (which for active electrode 176 isthe addition of all of the capacitive elements in parallel) illustratedin FIG. 59 (parasitic inductances LP are so small in value that they canbe ignored). When one compares this solid composite curve with that of aprior art feedthrough capacitor, one sees that the prior art feedthroughcapacitor outperforms the composite curve at frequencies above 1000 MHz.It will be obvious to those skilled in the art that one way around thiswould be to increase the capacitance value of the flat-through parasiticcapacitor so that it could start performing at a lower frequency. Aneffective way to increase the capacitance value of the parasiticcapacitor is to increase the dielectric constant of the surroundingdielectric materials. Referring back to dielectric substrate layers 226and 228 of FIG. 63, that would mean, for example, using a highdielectric constant (k) dielectric, such as barium titanate or strontiumtitanate for the insulative substrate material 234. This would raise thedielectric constant (k) up into the area above 2000. Accordingly, thevalue of the flat-through capacitance would go up so high that one wouldnot even need to include the MLCC capacitance. Another way to accomplishthe same thing and to use lower cost materials would be to use flexcable technology, such as polyimide or Kapton flex as previouslydescribed. The problem with this is that the dielectric constant ofthese materials is relatively low (typically below 10). However, one wayto make up for this would be to increase the effective capacitance areain the overlap area of the active electrode plates 176 and theirsurrounding sandwiched ground shields 194 and 194′ (and/or reduce thedielectric thickness, d).

FIG. 69 is an exploded view of the quadpolar hybrid EMI filter of thepresent invention that is similar to that previously shown in FIG. 63.In FIG. 69, the circuit layers 226 and 228 of FIG. 63 have been modifiedto add inductor traces 158-158′″. These inductor traces are included aspart of and are in series with active electrodes 176-176′″. It will beobvious to those skilled in the art that one would most likely selectone inductor pattern and stay with that. For example, in electrode plate176, there is a rectangular Wheeler spiral inductor 158. In electrodeplate 176′, we have by way of example, an inductor meander 158′ whichcan be one of many patterns, including those illustrated in FIG. 74. Inelectrode plates 176″ and 176′″, we have round Wheeler spiral inductors158″ and 158′″ as shown. Embedding co-planar inductors in series withthe active electrodes is virtually a no-cost addition. The reason forthis has to do with the manufacturing methods typically employed toproduce flex cables or even solid substrates. That is, a solid metallayer is laid over the entire surface by plating or othermetal-deposition processes and then resistive materials are laid down bysilk-screening or similar processes. Then chemical etchings are used toremove all of the metal except for the desired electrode patterns.Accordingly, once a setup is made, adding inductor elements 158-158′″ asshown in FIG. 69 becomes very inexpensive and easy to do. Advantages ofadding the inductors as shown in FIG. 69 include making the low-pass EMIfilter from a single element into what is known as a dual elementL-section low-pass filter. A dual element filter has a steeperattenuation slope and is therefore more efficient. There is anotheradvantage from adding the inductor shapes as shown in FIG. 69. By doingthis, one increases the ECA and therefore the parasitic flat-throughcapacitance at the same time. Therefore one ends up with a veryefficient distributive filter consisting of the inductance in serieswith the active electrode(s) and parasitic capacitances in parallel toground.

FIG. 70 is very similar to FIG. 69 except that the active electrodetrace layers 226″ and 228″ have been modified by adding an optionalsurrounding co-planar ground shield 224. This surrounding ground shieldconcept to prevent substrate edge re-radiation was previously describedin relation to FIG. 60. However, the difference in FIG. 70 is that anoptional co-planar ground shield 224′ has also been disposed on layers226″ and 228″ between each of the active electrode traces 176 and 176′and also 176″ and 176′″. For example, with reference to layer 226″ ofFIG. 70, one can see a co-planar ground shield 224′ that is disposedbetween circuit traces 176 and 176′. This would be used in the casewhere it was important to prevent cross-talk between adjacent circuittraces 176 and 176′. For example, this might be important in a cochlearimplant to keep each digital or analog voice channel that stimulates theauditory nerve free of distorting noise from an adjacent channel. Thisbecomes particularly important when the dielectric layer 226″ on whichthe circuit electrodes 176 and 176′ are deposited, are of high kdielectric materials. The use of high k dielectric materials increasesthe parasitic capacitance that would occur between circuit electrodelayers 176 and 176′. The presence of a co-planar grounded shield trace224′ prevents the cross-talk between the adjacent circuit traces. Thiscross-talk shield 224′ can be used in conjunction with, as shown in FIG.70, or without (not shown) with the surrounding edge shield 224. Thecross-talk shield 224′ also need not be used on all active electrodelayers in a particular shielded three-terminal flat-through EMI/energydissipating filter 190, but only in those layers where cross-talk is aconcern between adjacent circuits. In other words, the cross-talk shield224′ may be used on layer 226″ but not be needed on layer 228″. It willbe obvious to those skilled in the art that on a particular substratelayer, that the number of circuit active electrodes (and optionalcross-talk shields) is not limited to two (such as 176 and 176′ as shownin FIG. 70), but can be of any number, n.

FIG. 71 is yet another alternative to the quadpolar shieldedthree-terminal flat-through EMI/energy dissipating filter 190 aspreviously described in relation to FIG. 70. The difference between FIG.70 and FIG. 71 is the addition of a feedthrough capacitor 132 which isbonded to the hermetic terminal 112 by way of an insulative adhesivewasher 200. Feedthrough capacitors 132 are well known in the prior artand provide very effective high frequency filtering. FIG. 71 illustratesthat these prior art feedthrough capacitors can be used in combinationwith the novel shielded three-terminal flat-through EMI/energydissipating filter technology of the present invention. In a preferredembodiment, the structure as illustrated in FIG. 71 would allow for theelimination of the MLCC capacitors 142-142′″ as illustrated (or theycould be replaced by higher value MLCCs, film chip capacitors, tantalumtechnology or the like). In other words, there would be sufficientcapacitance from the feedthrough capacitor 132 in combination with theflat-through capacitances of the hybrid substrate electrodes such thatit is unlikely that additional filtering would be required for highfrequency (above 100 MHz) attenuation. However, if one were to desireextremely low frequency filtering, one could use a monolithic ceramicfeedthrough capacitor as illustrated in FIG. 71 along with the shieldedthree-terminal flat-through EMI/energy dissipating filter technology andsurface mounted very high capacitance value tantalum capacitors. Thiswould yield a filter that would be effective from all the way down inthe kHz frequency range all the way up through 10 GHz. For AIMDapplications, this would be very important for filtering for lowfrequency emitters such as those created from electronic articlesurveillance (EAS) gates or low frequency RFID readers (in the 125 to132 kHz or 13.56 MHz range). These EAS gates are the pedestals that aperson, including a pacemaker patient, typically encounters when exitinga retail store. These detect tags on articles and goods such as toprevent theft. One common system is manufactured by Sensormatic whichoperates at 58 kHz. It has been demonstrated through numerouspublications that these EAS gates can interfere with pacemakers andICDs. The present invention as illustrated in FIG. 71 would be effectivein attenuating signals at 58 kHz all the way up through cell phonefrequencies in the GHz range.

FIG. 72 is a blown up view of the round Wheeler spirals 158″ and 158′″of FIG. 69.

FIG. 73 is a square Wheeler spiral which is very similar to therectangular Wheeler spiral 158 previously shown in FIG. 69.

FIG. 74 shows some typical inductor meander shapes 158′. It will beobvious to those skilled in the art that any number of differentinductor shapes can be easily deposited on the same co-planar substratelayer in series and an integral part of the active electrode plate(s)176 of the shielded three-terminal flat-through EMI/energy dissipatingfilter 190 technology of the present invention.

The advantage of adding additional elements to a low-pass filter isdramatically illustrated by FIG. 75, which illustrates the attenuationcurves for various types of low-pass filters. By way of reference, atypical MLCC capacitor curve is shown. As one can see, the MLCCundesirably goes through a self resonant frequency SRF after which itsattenuation declines versus frequency (the MLCC undesirably becomesincreasingly inductive). However, for shielded three-terminalflat-through EMI/energy dissipating filters of the present invention,one achieves broadband filter performance all the way up to andincluding 10 GHz. As one can see, a single element or C section filterhas an attenuation slope of 20 dB per decade. When one adds a seriesinductor to this, as shown in the L section filter, the attenuationslope increases to 40 dB per decade. The addition of a third element,which makes the filter into either a .π or T section, increases theattenuation slope to 60 dB per decade. Going further, one could have adouble L, which is shown as a LL₁ or an LL₂, meaning that the inductorcan point either towards the body fluid side or to the device side, hasan attenuation slope of 80 dB per decade. One can add any number ofelements in this way. For example, a 5-element filter will have 100 dBper decade attenuation slope. It will be obvious to those skilled in theart that any number of elements could be used.

Referring once again to FIG. 69, the structure shown has an electricalschematic as shown in on FIG. 62 as an L section circuit. Thecapacitance of this L section consists of the sum of the parasiticfiat-through capacitance C_(P) which is formed between the activeelectrode plate 176 including the ECA formed from the inductors 158, andthe opposing grounded shields 194 and 194′. The MLCC capacitor 142 inFIG. 62 represents the capacitors 142-142′″ surface mounted onto thehybrid substrate 192. The MLCC capacitor is effective up to its resonantfrequency; however, that is where the flat-through capacitance takesover yielding the relatively smooth curve shown in FIG. 75 for the Lsection filter. It will be obvious to those skilled in the art that theL section could be reversed. In other words, the inductor spiral couldbe designed and put on the other side of the capacitor as opposed totowards the body fluid side as presently shown in FIGS. 61 and 62. Inaddition, it will be obvious to those skilled in the art that multipleinductors could be placed inside of the novel hybrid substrate 192 inorder to form a “π”, “T”, “LL” or even a “5” or “n” element device.Accordingly, the present invention includes a new method of constructingprior art low-pass EMI filter circuits that are already well known inthe art. In other words, the feedthrough capacitor, the L, the the T andLL filters are already well known. However, this is the first time, tothe knowledge of the inventors, that a flat-through capacitance has beenembedded within grounded shields 194 and 194′.

FIG. 76 is a family of filter attenuation curves similar to thatpreviously shown in FIG. 68. In FIG. 74, one can see that the 3 dBcutoff point, or the point at which the flat-through (C_(P)) curve ofthe shielded three-terminal flat-through EMI/energy dissipating filterstarts to become effective, has been moved substantially downward infrequency (to the left). In this case, its 3 dB point is approximately40 MHz. In addition, since it is now part of an L section filter, itsattenuation slope rate has been increased from 20 to 40 dB per decade.In FIG. 76, the referenced feedthrough capacitor curve is unchanged aswell as the MLCC curve (these are discrete component comparison curvesonly). However, the composite curve, which is the addition of the MLCCcurve, which is surface mounted to the shielded three-terminalflat-through EMI/energy dissipating filter substrate to the shieldedthree-terminal flat-through EMI/energy dissipating filter activeelectrode flat-through curve, is now substantially improved. At allpoints, the composite curve of the shielded three-terminal flat-throughEMI/energy dissipating filter with the surface mounted MLCC(s)outperforms (has higher attenuation than) the referenced prior artfeedthrough capacitor. In many cases, the amount of improvement is verysubstantial. For example, at MRI frequencies which are 64 MHz for 1.5Tesla machines and 128 MHz for 3 Tesla machines, there is an improvementanywhere from 10 to over 20 dB. This is very significant and veryimportant to protect an active implantable medical device frominterference during MRI scans.

FIG. 77 illustrates a bipolar hermetically sealed hybrid substratefilter 190 of the present invention.

FIG. 78 is an exploded view of the internal layers taken along line78-78 in FIG. 77. One can see that in active electrode plates 176 and176′, the square Wheeler spirals 158 and 158′ have been greatlyenlarged. In order for the grounded shield plates 194-194″ to be properEMI shields and RF grounds, it is essential that they be properlygrounded via electrical connection material 210-210″ to the gold brazering 124 of the ferrule 120 of the hermetic seal 112 as shown in FIG.77. For AIMDs, ferrule 120 is typically of titanium, stainless steel orsuitable non-corrosive material. Unfortunately, during manufacturing orover time, titanium can build up undesirable oxides. These oxides canact as an electrical insulator or even a semi-conductor. Attachment ofelectrical components to this oxide can cause undesirable circuitbehavior. In the case of a low-pass EMI filter, this can causedegradation of the EMI filter performance. Therefore, it is essentialthat a connection be made to a non-oxidizing surface. Fortunately, thepresence of gold braze 124, as shown in FIG. 77, forms a convenientnon-oxidizable surface for such attachment. Attachment to this goldbraze is described in U.S. Pat. Nos. 7,038,900 and 7,310,216 thecontents of which are hereby incorporated by reference.

In FIG. 77, one can see that there is an electrical connection material210″ that connects between metallization band 222 and the gold brazematerial 124. On the opposite side, there is a similar electricalconnection 210 that is made between metallization band 222′ and the samegold braze material. On the left hand side of the hybrid substrate 192,electrical connection material 210′ is also connected from metallizationband 208 and the same gold braze material 124. One can also see this inthe exploded view of FIG. 78 by looking at the electrical connections210-210″ for the ground shields layers 194-194″. In this case, this isknown as a three point ground system which forms an adequate (but notideal) RF ground for the present invention. The more contact there isbetween these electrical attachments 210-210″, the better. This isbecause as one increases the contact area to the grounded shield plates194-194″ it will reduce the electrical impedance and therefore improvetheir shielding efficiency, particularly at high frequency.

FIG. 79 is an alternative embodiment showing the hybrid substrate 192 ofthe present invention designed to be inserted partially into the ferrule120 of the hermetic seal assembly 112 as shown in exploded view. Thereare convenient wire bond or electrical connection pads 139-139″″ asshown. In this case, 139″″ would be a ground pad, and pads 139-139′″would be circuit connections. The MLCC capacitors 142-142′″, aspreviously described, would connect from the active electrode plates(not shown) of the shielded three-terminal flat-through EMI/energydissipating filter through vias internally to internal grounded shieldplates (also not shown). As previously described, if enough flat-throughparasitic capacitance can be generated within the hybrid substrate 192,then the MLCC capacitors 142-142′″ would not be required. Also shown isan optional embedded Wheeler spiral inductor 158. There would be one ofthese in series with each of the MLCC capacitors 142-142′″ as previouslydescribed. A shield ring 242 is provided so that it will be connectedthrough laser welding, brazing, soldering or the like to the ferrule120. This is important so that electromagnetic interference cannotdirectly penetrate through the insulator 118 and re-radiate to theinterior of the electronic device (a hermetic insulator forms a hole inthe titanium electromagnetic shield housing of a cardiac pacemaker). Theshield ring 242 is connected via soldering to via holes to the internalground shield plates of the shielded three-terminal flat-throughEMI/energy dissipating filter structure. Connection pads 240 through240′″ are designed to be electrically connected to lead wires 114through 114″.

FIG. 80 is a partially fragmented view taken from FIG. 79. In this case,the leads 114″ and 114′″ are typically welded, brazed or soldered 244and 244′ into the lead wire retaining blocks 240″ and 240′″ as shown.One can also see that there is an optional electrical connection 246 and246′ inside of the flange 120 of the hermetic seal 112. This electricalconnection makes contact to the internal grounded shield plates (notshown) of the hybrid substrate 192. One can see that the electricalconnection material 246 and 246′ not only makes contact to the titaniumflange 120, but it also makes intimate contact to the gold braze 124such that there is an oxide free electrical connection in order toguarantee high frequency performance. In FIG. 80, one can see that theexternal shield ring 242 has been eliminated and replaced by ametallization layer 247. The metallization area 247 forms acircumferential ring over the non-conductive insulator 118 such thatre-radiation of EMI through the hermetic seal 112 is prevented.

FIG. 81 is the electrical schematic diagram of the quadpolar hybrid EMIfilter of FIGS. 79 and 80. FIG. 81 illustrates an L-section low-passfilter.

FIG. 82 illustrates an inline hybrid substrate 192 of the presentinvention. In this case, there are internal grounded shield plates (notshown) that have already been well described. There are multipleelectrical connection points to the gold braze 124 consisting of210-210″″. In this case, back-to-back MLCC capacitors 142 and voltagesuppression diodes 248 (also known as zener diodes) have beenincorporated in parallel. This is best understood by referring to theelectrical schematic diagram of the structure shown in FIG. 83. Startingfrom the outside of an electronics module of the body fluid side of anAIMD (on the left), one can see that as EMI enters, it first encountersa flat-through capacitance CP in accordance with the novel throughelectrodes of the shielded three-terminal flat-through EMI/energydissipating filter of the present invention. Then, as you move to theright in FIG. 83, the EMI encounters an inductance L₁ which is typicallyfrom an embedded co-planar Wheeler spiral inductor (not shown) containedwithin the active electrode plates of the hybrid substrate 192. Then itencounters the parallel combination of the MLCC capacitor 142 and thehigh voltage suppression diode 248. Then there can be another inductor(optional) L₂ that would be embedded within the hybrid substrate 192 andan additional flat-through capacitance C_(P′) before one reaches theelectrical connection pads a through g as illustrated.

Referring once again to FIGS. 82 and 83, the inductors, for exampleinductor L_(1a) and L_(2a), could be constructed of square, rectangularor a round Wheeler spirals or any of the other meander shapes previouslydescribed. FIG. 83 illustrates a very efficient five element low-passfilter.

FIG. 84 illustrates another form of the novel hybrid substrate 192 ofthe present invention. The shielded three-terminal flat-throughEMI/energy dissipating filter includes a hybrid substrate 192 is dividedinto two sections: 192′ and 192″. Section 192′ is a relatively thin areaof flex cable and is therefore very flexible. Section 192″ can be madeof similar or same materials as section 192′ (or it can be a rigid boardor substrate to which flexible section 192′ is connected), but itsthickness is built up until it forms what is known in the art as asection of “rigid” cable. This rigid section 192″ could be of polyimide,Kapton or other typical flex cable construction. It will also be obviousto those skilled in the art that this could also be a piece of rigidmultilayer substrate or circuit board, including any of the ceramics orFR4 board or the like. The flex cable section 192′ is designed to slipdown over the pins 114-114′″ of a hermetic seal 112 of an AIMD or anyother electronic device (hermetic or not), such as those typically usedin telecommunications, consumer electronics, military or even spaceapplications). The hermetic seal 112 can be any type of terminal,including non-hermetic terminals or even plastic terminals. The presentinvention is applicable to any electronic assembly or a point at whichany lead wires ingress and egress an electronic assembly, subassembly orhousing. The methods of attachment to the terminal pins 114-114′″ of thehermetic seal 112 and to the ground pin 196 will be described inconnection with subsequent drawings.

Referring now to the rigid section 192″, one sees that a number ofpassive or active surface mounted electronic components can be mounted(they can also be embedded which is also well known in the prior art ofmultilayer substrate design). In this particular case, the hybridsubstrate 192 of FIG. 84 has been designed with convenient lead wires204-204′″ and 196 for easy connection to lands of a circuit board 250perhaps with an integrated circuit or microchip 252 within the activeimplantable medical device. The circuit board 250 is not part of thepresent invention, but is important in that the present invention becapable of connecting and interfacing with it.

FIG. 85 is very similar to FIG. 84 except the diode array D₁ has beenreplaced with either a passive or an active RFID chip (RFID). In thepreferred embodiment, this would be a low frequency passive RFID chipmeaning that it would operate at a frequency that could easily penetratethe titanium electromagnetic shield of a typical AIMD or other EMIshielded electronic device. In a preferred embodiment, the RFID chipwould operate in the International Standards Organization (ISO) band of125 to 135 kHz. The RFID chip could be used for a number of differentpurposes, including identification of the model number, serial number ofthe AIMD, important patient or implanting physician information and thelike. See U.S. Patent Application Publication No. US 2006-0212096 A1,the contents of which are incorporated herein by reference.

The RFID chip as illustrated in FIG. 85 could be simply mounted but notelectrically connected to the active electrodes of the shieldedthree-terminal flat-through EMI/energy dissipating filter. No electricalconnections are required for a passive RFID chip. In other words, whenan external interrogator/reader was used, a powerful electromagneticfield would activate an antenna within RFID chip and it wouldautomatically use the received power to turn on its microchip andtransmit a return pulse. However, in another embodiment, the RFID chip,as shown in FIG. 85 could be electrically connected to power circuitsembedded within the shielded three-terminal flat-through EMI/energydissipating filter such that it received power from the internal batteryof the AIMD. In this case, it would be known as an active RFID chip.With an active (powered) RFID chip, it could embody a much moresensitive receiving circuit and also transmit a much more powerfulreturn pulse. In another embodiment, the RFID chip as shown in FIG. 85could be used as a wake-up feature for AIMD RF telemetry circuits.

In the past, pacemaker and ICD and neurostimulator telemetry was done byclose-coupled magnetic coils. In this older art, it was typical that theAIMD would have a multiple turn wire antenna within the titanium housingof the AIMD. There were even AIMDs that use an external loop antenna ofthis type. To interrogate or reprogram the AIMD, the physician or othermedical practitioners would bring a wand, with a similar antennaembedded in it, very close to the AIMD. For example, for a typicalpacemaker application, the telemetry wand would be placed directly overthe implant with a wire connected to an external programmer. The medicalpractitioner would move the wand around until the “sweet-spot” waslocated. At this time, the external programmer would become active andelectrograms and other important information would be displayed.Typically, the wand would be right against the patient's skin surface orat most a couple of centimeters away. In the last few years, distance RFtelemetry is becoming increasingly common. In this case, for example fora cardiac pacemaker, there would be a high frequency antenna that wouldbe embedded within the plastic header block of the AIMD (outside the EMIshielded titanium housing). This would communicate with an external RFreceiver-transmitter programmer. A typical band for such communicationwould be in the 402 to 405 MHz (known as the MICS band). Other devicesuse even higher frequencies for distance RF telemetry. A problem withsuch distance telemetry circuits is the energy consumption of thereceiver circuitry which must be on all the time. There is onemethodology which is known in the art as the Zarlink chip. The Zarlinkchip uses a higher frequency (in the GHz range) to wake-up the lowerfrequency RF telemetry circuit. The higher frequency is more efficient;however, the device or chip still consumes an amount of idling energyfrom the AIMD battery to always be alert for its wake-up call. Analternative of this resides in the present invention where a passiveRFID chip is used as a wake-up feature. This RFID can be integrated intothe hybrid substrate 192 of the present invention (or mounted anywhereelse inside or outside the housing of the AIMD). In a preferredembodiment, the external RF programmer can incorporate a low frequencyRFID reader which would transmit a signal which would penetrate rightthrough the titanium housing of the AIMD and activate the embeddedpassive RFID chip. The circuitry of the RFlD chip would be connected tothe telemetry circuits contained within the AIMD. For an example, in thecase of a pacemaker, the external programmer would send the RFID signalas a wake-up call to turn on the telemetry receiving circuits so thatthe pacemaker could communicate with the external programmer.

FIG. 86 is very similar to FIG. 84. In this case, toroidal inductorsL3-L3′″ have been used to replace the surface mount chip inductors. Chipinductors are low in both their inductance value and their currentrating. Chip inductors can be acquired in two main forms: a) with aferrite core, and; b) without a ferrite core. For exposure in MRIapplications, it is usually desirable to eliminate ferrite material asit will saturate due to the main static field of the MR scanner. SeeU.S. Patent Application Publication No. US 2007-0112398 A1 and U.S. Pat.No. 7,363,090, the contents of which are incorporated herein. In FIG.86, one can see that the toroidal inductor L3′ does have a ferrite coreTC with many turns of wire W wrapped around it. This makes for a verylarge inductor value. However, as mentioned, in an MRI environment, theinductance would drop to a very low value due to the saturation of theferrite element TC itself. It is a feature of the present invention thatthe ferrite element would be selected so that it would not exhibitpermanent remnants. That is, once the device was removed from themagnetic resonance (MR) scanner, the magnetic dipoles would return totheir scattered state and the inductor would continue to operate aspreviously intended. The purpose of the toroidal inductors L3-L3′″ wouldbe to provide a very high inductance value for a low-pass filter so thatits 3 dB cutoff frequency would be very low in frequency (for example,below 1 MHz or even down to 58 kHz for EAS gates). In fact, it will beobvious to those skilled in the art that inductor chips could also belarge value wound inductors with powdered iron or ferrite toroidalcores. In an MR scanner, the electromagnetic field environments arequite harsh, but are also well known. For example, for a 1.5 Teslascanner, the pulsed RF field is at 64 MHz. Accordingly, the shieldedthree-terminal flat-through EMI/energy dissipating filter could bedesigned such that its parasitic flat-through capacitance along withMLCC capacitors C₂ would provide sufficient attenuation at 64 MHz sothat the AIMD could be free from EMI and be operated safely in an MRscanner. Accordingly, it would not matter that the cores of the toroidalinductors 156 saturated and that low frequency filtering is thereby notavailable during the time of the MR scans. Obviously, a person in an MRscanner is not likely to encounter an EAS gate or RFID reader typicallyfound when exiting retail stores. What is important is that after thepatient is removed from the MR scanner is that the toroidal inductors(or chip inductors with ferrite cores or layers) not exhibit permanentremnance and return to their original state so that they will continueto provide effective low frequency filtering against emitters that thepatient may find in their every day environment.

FIG. 87 illustrates the flexibility of section 192′. As one can see, itis very easy to bend the entire flex section 192′ into a right angle.This is important so that the entire assembly can easily fit inside thetypical spaces and geometries of active implantable medical devices,including cardiac pacemakers and the like.

FIG. 88 is an internal sectional diagrammatic view taken of the hybridsubstrate 192 of FIG. 84. In FIG. 88, one can see that the gold braze124 of the hermetic seal 112 is shown on the left. An electricalconnection BGA is made between internal ground via V to shield plates194 and 194′ and the gold braze material 124. These electrodes/RF shieldplates 194 and 194′ extend full width throughout the flexible portion192′ and the rigid portion 192″ as illustrated in accordance with thepresent invention. Other circumferential via holes V (not shown) areused to provide a low impedance attachment to additional points betweenground shield plates 194 and 194′ to the gold braze 124 of the hermeticseal as shown. There are also additional ground shields connected by viahole V₂ to optional/additional RF shields plates 194″-194″″ as shown. Aspreviously mentioned, it is very important that the electricalconnection BGA to the gold braze 124 be multi-point connections in suchthat a very low impedance is achieved so that the ground shields canproperly function as a faraday cage shield at high frequencies.

Starting from the left and moving along to the right on FIG. 88, we willnow follow flat-through capacitor active electrode plate 176. On theleft side, active electrode plate 176 is electrically connected to leadwire 114 from the hermetic terminal by means of via hole and eyelet V₁.For simplicity, we are only going to trace one of the quadpolar circuits176, although it will be obvious to those skilled in the art that theother three are of similar or identical flat-through capacitorconstruction techniques described herein. Parasitic flat-throughcapacitances C_(P) are formed due to the ECA that is formed along thelength of active electrode plate 176 which is sandwiched between theopposed grounded shield plates 194 and 194′. Via holes V₂, V₃, V₄, V₅V₆, and V₁₃ (and others not shown) are part of a multipoint groundsystem so that the ground plates 194 and 194′ are kept at the same lowimpedance shield potential.

Going further to the right, one encounters via hole V_(x) and V_(y)which connect MLCC 142 in parallel with inductor chip 156 forming anovel resonant tank filter for attenuating MRI RF signals and the likeas previously described in U.S. Pat. No. 7,363,090, and U.S. PatentApplication Publication Nos. US 2007-0288058 A1, US 2008-0071313 A1, US2008-0049376 A1, US 2008-0161886 A1, US 2008-0132987 A1 and US2008-0116997 A1, the contents of which are incorporated herein byreference. As one can see, this parallel combination of inductor chip156 and chip capacitor 142 form a parallel combination which iselectrically in series with active electrode plate 176 in accordancewith the referenced co-pending patent serial numbers. Having MLCC 142and inductor chip 156 placed on opposite sides (top and bottom) of thehybrid substrate 192 is just one way to form the parallel resonantcombination. For example, if one refers to FIG. 80, 85 or 87 of U.S.Patent Application Publication No. US 2007-0112398A1, any of these novelintegrated L-C chips could be used as a single element on top (or thebottom) of hybrid substrate 192 that would replace both MLCC 142 andinductor 156. It will be obvious to those skilled in the art that theparallel bandstop filter formed by C₁ and L₁ can be placed anywhere inthe active electrode circuit of the shielded three-terminal flat-throughEMI/energy dissipating filter. In other words, it could be moved furtherto the right, for example, after L₂ or even after L₃. It will also beobvious to those skilled in the art that any combination of circuitelements is possible, including placing circuit elements 142 and 156 inseries as an inductor-capacitor (L-C) trap filter anywhere between theactive electrode 176 and ground 194, 194′.

Referring once again to FIG. 88, active electrode plate 176 is thenrouted through via hole V₇ through inductor L₂ and then back downthrough via hole V₈ back to active electrode plate 176. Active electrodeplate 176 is then electrically continuous to another via hole V₉ whichis connected to the right hand termination surface of MLCC capacitor C₂.The other termination end of the capacitor C₂ is connected through viahole V₄ to grounded shield substrates 194-194′″. This makes for a verylow impedance RF ground connection for capacitor C₂. The activeelectrode plate 176 then continues to via hole V₁₀ and up and to theright through inductor L₃ whose other end termination returns throughvia hole V₁₁ putting L₃ in series with active electrode plate 176. Aspreviously described, inductors L₂ and L₃ can be chip inductors,including ferrite chip inductors or they can be toroidal wound inductorsor other types of inductors. Active electrode plate 176 is thenconnected through via hole V₁₂ to the right hand side of the highvoltage suppression diode array D₁. The left hand side of the diodearray D₁ is connected through via hole V₁₃ such that it makes connectionwith grounded shield plates 194-194′″. Active electrode plate 176 thenexits to the right from via hole V₁₂ over to via hole V₁₄ and then up towire bond pad 138 which is very convenient for connection of lead wire204 as shown. A ground pad GP on top of the hybrid substrate 192 hasbeen provided which connects by via hole V₆ to the embedded groundedshield plates 194-194′″.

Referring now back to FIG. 84, one can see ground wire 196 which hasbeen connected to the bond pad area GB. This is not required for allAIMDs, however, it is a very convenient point for connection ofintegrated circuit substrate 250 ground circuit trace or traces to thehousing of the AIMD via lead 196 and then to the ground shield plates194, 194′ of the hybrid flex shielded three-terminal flat-throughEMI/energy dissipating filter. As previously described, the groundshield plates are connected to the gold braze 124 of the hermetic seal112 which is typically laser welded into the overall titaniumhousing/can of the AIMD (shown as 300 in FIG. 114). The housing can actas an EMI shield, an electrode or an energy dissipation surface. In allcases, a low impedance RF ground is required which is accomplished bythe grounded shield plates of the shielded three-terminal flat-throughEMI/energy dissipating filter 190 of the present invention. Referringback to FIG. 88, one can see that there are a number of parasiticflat-through capacitances C_(P) that are formed in accordance with thepresent invention between shield plates 194 and 194′ which surroundactive electrode plate 176 on top and bottom as shown.

FIG. 89 is the schematic diagram of the novel hybrid substrate 192 ofFIG. 84. For example, tracing one of the quadpolar circuits through, forexample the circuit labeled 176, point “a” is toward the body fluid sideof the lead wire 114 that connects from the hermetic seal 112 shown inFIG. 84. Typically, this would connect through a connector block ordirectly to a lead system where an electrode would come into contactwith body tissue (in a unipolar pace or sense mode, the AIMD housing/canwould serve as the return electrode). On the opposite side of thehermetic terminal, we have the same lead wire 114 which then connects tothe via hole V₁ of the flexible hybrid substrate 192′. The activeelectrode plate 176 enters the bandstop filter BSF which consists of theparallel inductor L₁ and MLCC capacitor C₁, one sees that we have nowentered the shielded part of the substrate meaning that the entireactive electrode plate 176 is contained within grounded shield plates194 and 194′. After exiting the bandstop filter BSF, we then go throughinductor L₂, and then MLCC capacitor C₂ is connected to ground 194,194′. MLCC C₂ is then connected with inductor L₃. After active electrode176 exits inductor L₃, it is still shielded/sandwiched within the groundplates 194, 194′ of the hybrid substrate 192. We then encounter thetransient voltage suppression diode array DA. In this case, the diodearray is shown connected to ground and acts as a high voltagesuppression device. Diode arrays DA of this type are commonly used inAIMDs. The reason for this has to do with the use of either ICDs orautomatic external defibrillators (AEDs). AEDs are now commonly deployedin government buildings, hotels, airplanes, and many other publicplaces. These life saving devices are very important. If a person isunconscious, the AED electrodes are placed on the person's chest. TheAED then automatically detects dangerous ventricular arrhythmias (suchas ventricular fibrillation) and then an automated high voltage biphasicshock is applied to the electrodes. If the person has an implantedpacemaker (which is often the case) then the implanted leads pick upthis high voltage shock that is being used to cardiovert the cardiactissue. Since the implanted pacemaker is a low voltage device, this highvoltage shock can damage sensitive internal circuits of the cardiacpacemaker. Accordingly, diode arrays, incorporating back to back diodes,zener diodes, transorbs or the like are commonly used to short the highvoltage spike to ground before it can damage sensitive active electroniccircuits (such as integrated circuits, hybrid chips and the like). Sincethe diode array that's typically used takes up a lot of space on thecircuit board, it is a feature of the present invention that it couldeasily be integrated into the shielded three-terminal flat-throughEMI/energy dissipating filter 190 of the present invention to save spaceby placing it on the interconnect circuit. We then exit the novel hybridsubstrate 192 of the present invention at point “a” and make anelectrical connection to the IC wire bond pad 139 as shown. Another wayto think of the schematic diagram shown in FIG. 89 is that what we haveis a bandstop filter for suppression of MRI or other powerful singlefrequency emitters in series with a three element T section filter aspreviously described in connection with FIG. 73 in series with a highvoltage suppression diode. It will be obvious to those skilled in theart that the bandstop filter could be located to the right of the C, L,π, T or .eta. element filter. It could also be placed in combinationwith L-C trap filter to ground. Accordingly, one can see that a numberof components have been assembled into one convenient package.

Referring back to FIG. 84, there are a number of other features of thenovel hybrid flex substrate 192 that need to be pointed out. One of thefeatures is best described by referring back to FIG. 84 wherein the viaholes have an enlarged rectangular portion A, B, C and D for suitableelectrical probing or electrical testing. This section allows for arobot or a pogo spring connector to be placed on the pad to facilitateelectrical testing, accelerated life testing, burn in, insulation test,dielectric withstanding voltage test or other suitable electrical testsas needed. These tests, often performed at elevated temperatures, areessential to assure the long term reliability of the novel shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention. In the opposite (right) end of the rigid part of thesubstrate 192″, a similar enlarged pad area(s) 139 has been provided forsimilar electrical contact for test instruments as previously described.For ease of manufacturing, it is also convenient that the entire hybridflex substrate 192 be laid flat as is shown. Being laid flat isparticularly suitable to be placed into fixtures for modern robots.These robots are typically fed by tape and reel components or trayswhich house all of the electronic components. By having the basic hybridsubstrate 192 laying flat, all of the components can be quickly placedby the robots. Assembly by hand is impractical due to the small size ofthe surface mounted components. For example, the MLCC chips can be 0201or smaller which is the size of a grain of pepper (0.020 inch by 0.010inch). It is then a matter of prior art wave-soldering or equivalenttechniques to make the electrical and mechanical connections to all ofthe components. This is followed up by automated optical inspection,electrical test and even X-ray if needed.

Again referring to FIG. 84, so that adequate electromagneticinterference protection will be provided to sensitive AIMD electronicsand sense circuits, the inductor L₂ will preferably be of a non-ferritecore and the capacitor C₂ would be of sufficient value working inconjunction with flat-through capacitance C_(P) such that thosecomponents alone would provide adequate protection at MRI pulsedfrequencies. For example, for 1.5 Tesla MR scanner, the RF pulsedfrequency is 64 MHz. It would be desirable for component C_(P), L₂ andC₂ to have over 40 dB attenuation at 64 MHz to provide adequateprotection to device electronics. With the use of a very high valueinductor L₃, as illustrated in FIG. 86, one can provide a very highdegree of (attenuation) immunity to low frequency emitters, such as 58kHz electronic article surveillance (security) gates that are typicallyused in retail stores. In addition, one can provide a great deal ofimmunity to low frequency (LF) RFID readers. These are typically usedfor automotive keyless entry systems and the like. Since neither RFIDreaders nor store security gates are present in an MR scan room, it doesnot matter if inductor L3′ does saturate in the MR environment.Accordingly, a novel methodology is provided in the hybrid substrate 192such that certain filter components do not saturate during the MR scanand others do. It will be obvious to those skilled in the art thatcapacitor elements C₂ could be a monolithic ceramic capacitor (MLCC), ora very high value aluminum electrolytic or tantalum capacitor. In otherwords, for very low frequency filtering, a capacitor of severalmicrofarads could be used with a toroidal wound inductor of severalhundred microhenries. This would provide attenuation down to very lowfrequencies.

In FIG. 89, one can see that L₂ working in combination with C₂ and L₃form what is known in the art as a low-pass “T” filter. Any combinationof active or passive circuit elements can be readily adapted to theshielded three-terminal flat-through EMI/energy dissipating filter ofthe present invention. This includes any of the low-pass filter circuitsshown in FIG. 75, and any combinations of L-C traps and/or bandstopfilters (BSFs). It is a feature of the present invention that the threeterminal flat-through capacitance obtained by sandwiching large surfacearea through electrodes between surrounding ground plates result in aflat-through capacitance suitable to compensate for the self resonancecharacteristic (see FIG. 18) of prior art (and very low cost) MLCCs andallow them to be used in combination with the shielded three-terminalflat-through EMI/energy dissipating filter of the present invention toachieve a very broadband and effective EMI filter and highly effectiveenergy dissipater.

Referring again to FIGS. 85 and 88, it will be appreciated that thebandstop filter, which consists of C₁ in parallel with L₁, is completelyoptional. Also, the other circuit board filter components, such as the Tcircuit filter components L₂, C₂ and L₃ of FIG. 88 are also optional.For example, both inductors L₂ and L₃ could be eliminated meaning thatthe filter would be a single element filter consisting of the MLCCcapacitor C₂. One is further referred to the low pass filter curves ofFIG. 75, which can all be implemented into the novel circuit board ofthe present invention, as illustrated in FIG. 88 with its correspondingschematic of FIG. 89. Additionally, in FIGS. 88 and 89, the T circuitconsisting of L₂, L₃ and C₂ is illustrated in the family of low passfilter curves illustrated in FIG. 75. In this case, the T filter isindicated by L₁, C, L₂. Referring once again to FIGS. 88 and 89, byeliminating the bandpass filter consisting of C₁ and C₂, one couldimplement any of the filter circuits shown in FIG. 75, which in thesimplest form, includes a single MLCC chip capacitor as shown in thelower right-hand corner of the family of curves.

FIG. 90 is an electrical schematic for one circuit A of FIG. 86. In thiscase, the T circuit low-pass filter has been replaced with a circuitlow-pass filter consisting of C₂, L₂ and C₃. In FIG. 90, the bandstopfilter BSF consisting of components L₁ and C₁ acting in parallel, hasbeen replaced by a L-C trap filter consisting of L₁ and C₁ that arewired in series to ground 194, 194′. It is well known that when L-Cseries components are in resonance; they ideally form a short circuit atthe resonant frequency. This is more thoroughly described in U.S. Pat.No. 6,424,234 the contents of which are incorporated herein. Referringonce again to FIG. 90, when one is designing the trap circuit, one hasto be very careful of the parallel action of C_(P) and C₂. One has tomodel the circuit very carefully to make sure that the trap filterfunctions properly in the presence of these parallel capacitances. It isoften desirable, and well known in the art, to isolate the L-C trapfilter with a series bandstop filter so that it will not interact withother parallel capacitances. It will be obvious to those skilled in theart that a bandstop filter could be inserted on one or both sides of thetrap filter or between multiple trap filters to increase its or theirefficacy.

Referring once again to FIG. 90, the use of a trap filter would beparticularly advantageous if the AIMD were to be exposed to a MRIenvironment. For example, if the system were designed to be used in a1.5 Tesla scanner, the trap filter could be designed to be resonant at64 MHz. This would short out 64 MHz signals to ground (the titaniumhousing of the AIMD). This would not only provide a great deal ofimmunity and protection to device electronics, it would also desirablyshort MR energy to the metallic housing of the AIMD such that it cannotreflect back and cause overheating of the distal electrode tip to tissueinterface. Using the housing to dissipate energy is described in U.S.Provisional Patent Application No. 61/144,102, the contents of which areincorporated herein.

Referring once again to FIG. 90, the Pi (π) could consist of an MLCCcapacitor C₂ which would be very effective at high frequencies. L₂ couldbe a toroidally wound inductor with a ferrite core as previouslydescribed as L_(3′) from FIG. 86. C₃ could be a high value tantalumcapacitor. It would not matter if the 7 circuit was effective while theAIMD was operating in a MR scanner. This is because the L-C trap wouldbe made of components which do not saturate in a magnetic fieldenvironment. In other words, inductor L₁ would be non-ferromagnetic andcapacitor C₁ would generally be of MLCC construction. Therefore, the EMIfiltering immunity for the MR environments would consist entirely of theoperation of the trap filter operating in combination with the parasiticcapacitance (flat-through capacitance) of the novel hybrid substrate 192of the present invention. Accordingly, the it section filter would bevery effective when the patient is outside of MR environments forattenuating low frequency signals and signals throughout the frequencyrange. In other words, the structure as illustrated in FIG. 90 wouldperform effective filtering from approximately 30 kHz all the way to 10GHz while outside of an MR environment. While in an MR environment, itwould perform effective filtering at selected frequencies of one or moretrap filters as shown. Only one trap filter is shown, but it will beobvious to those skilled in the art that any number of trap filterscould be placed in parallel in order to short circuit multiple RFfrequencies. For example, if one were to want the AIMD to be compatiblewith both 1.5 and 3 Tesla scanners, then two trap filters would berequired; one resonating at 64 MHz and the other one at 128 MHz. Again,as previously stated, the L-C trap filter can each be separated by aseries bandstop filter consisting of a capacitor in parallel with aninductor so that the components of each individual trap filter do notinteract with each other.

Reference is made to U.S. Provisional Patent Application Ser. No.61/144,102, which describes a number of other frequency selectivecircuits that can be used to balance the energy during MRI scanning. Theobjective is to take as much energy off the implanted lead system andshunt it to the conductive housing of the AIMD which then becomes itsown energy dissipating surface. It will be obvious to those skilled inthe art that any and all of the schematics that are disclosed in U.S.Provisional Patent Application Ser. No. 61/144,102 can be embodied inthe novel hybrid substrate 192 of the present invention.

FIG. 91 is very similar to FIGS. 84, 85 and FIG. 86. The difference isthat a prior art feedthrough capacitor 132 is being used in conjunctionwith the hybrid substrate 192 of the present invention. Feedthroughcapacitors are well known in the prior art, including U.S. Pat. Nos.4,424,551; 5,333,095; 5,905,627; and 6,765,779, the contents all ofwhich are incorporated. Referring once again to FIG. 91, the feedthroughcapacitor 132 would provide high frequency filtering generally in thefrequency range from 100-10,000 MHz. As described for FIG. 86, the otherboard mounted components could then all involve very high capacitancetantalum or aluminum electrolytic capacitors, or toroidal inductorsusing high permeability ferrite cores. For example, feedthroughcapacitor 132 would provide sufficient immunity during an MRI scan suchthat the other components could all saturate. This would provide a veryeffective broadband filter operating generally in the frequency rangefrom 10 kHz all the way to 10 MHz.

FIG. 92 illustrates the reverse side of the flexible portion 192′ of thehybrid flex from FIG. 84. One can see that a robot has dispensed acircular portion of thermal-setting conductive thermal setting adhesive254. This is designed to align precisely with the gold braze 124 of thehermetic terminal 112 of FIG. 84. Accordingly, the entire substrate canbe laid down over the hermetic terminal assembly 112 and then thethermal-setting conductive material 254 can be cured in an oven, furnaceor other equivalent process. This makes a suitable electrical andmechanical connection to the exposed ground shield electrode plate 194′.Referring back to FIG. 92, one will see that there are gaps left in thecircumferential thermal-setting conductive polymer 254. These gaps arepresent to allow for a free flow of helium during fine leak detection aspreviously described. There are also via holes V₁, V₂, V₃ and V₄ whichare used to connect to the other internal ground shield plates,including plate 194.

FIG. 93 is a sectional view taken along line 93-93 from FIGS. 84 and 92.One can see the electrical connection formed by thermal-settingconductive adhesive 254 between via hole V₃ and the gold braze 124, forexample. Alternative methods of performing this low impedance RFelectrical ground connection to the grounded shield plates 194, 194′ ofthe shielded three-terminal flat-through EMl/energy dissipating filterof the present invention are illustrated in FIGS. 94 through 97.

FIG. 94 illustrates a methodology of pushing a resistance weldingelectrode pad 256 onto a flex cable rivet eyelet 258 thereby creating acurrent flow in which an elevated temperature results sufficient toreflow a low temperature braze 260 solder or the like to the gold brazematerial 124.

FIG. 95 illustrates an outer pin 262 which has been laser welded to theferrule 120. The minimum number of pins is one, but an optimal numberwould be four to six to provide suitable RF connection to the internalgrounded shield plates 194 and 194′ of the present invention.

An alternative method is shown in FIG. 96 wherein a series ofcounterbores or countersinks 264 have been provided in the top of theflange 120 such that multiple lead wires 196 could be placed along withgold braze rings 266. A high temperature brazing furnace is used toreflow the gold preforms 266 and electrically and mechanically attachthe pins/leads 196 to the ferrule 120. In this way, a number of groundpins 196 would be sticking up such that open via holes of the flexibleportion 192′ of hybrid substrate 192 of the present invention could belaid down and electrically attached to the grounded shield plates 194,194′.

Another RF ground attach methodology is shown in FIG. 97 wherein theferrule 120 is of a pressed powder metallurgy. In this case, a pedestalpin 268 (4 to 6 or omore is the ideal number of pedestals) is formed aspart of the powder metallurgy process. In this case, all the materialswould be typically of titanium which is ideal for this purpose. Becauseof the problems with titanium oxide formation, a gold sputtering 270,plating or brazing is placed over the terminal pedestal 268 such that aproper oxide-free electrical connection can be made to the hybridsubstrate 192 of the present invention.

FIG. 98 shows a modified version of the flexible portion 192′ of theflex cable assembly of FIG. 84 with four (or more) via holes VH suitablefor placement over any of the embodiments described in FIGS. 95 through97 for electrical attachments to its grounded shield plates 194 and194′.

FIG. 99 illustrates a cross-section 99-99 from FIG. 93 of yet anotherembodiment illustrating attachment of the active electrodes of substrate192′ over a terminal pin 114 along with some sort of a weld ring 272 ora braze ring. An electrical connection with weld or solder material 274is shown.

FIG. 100 illustrates another methodology wherein the lead wire 114 aspreviously shown in FIG. 84 could be bent over and then a lowtemperature braze 260 can be formed to an enlarged eyelet 276 of thenovel hybrid flex substrate 192.

FIG. 101 illustrates a novel laser weld cap 278 with a cut out section280. The cut out area 280 is formed or cut so the metal cap 278 can slipdown over the narrow section 192′ of the flexible portion of theshielded three-terminal flat-through EMI/energy dissipating filter. Thelaser weld cap 278 can be a stamped titanium, machined titanium,injection molded titanium or a number of other metals.

FIG. 102 is a combined cross-section taken generally from 102-102 fromFIG. 101 and also from section 102-102 from FIG. 84. However, the hybridsubstrate 192 has been modified to accommodate the novel laser weld cap278 as illustrated in FIG. 101. In FIG. 102 one can see that the laserweld cap 278 is slipped down such that it comes into close contact withthe flange 120 of the hermetic terminal 112. A continuous ordiscontinuous laser weld or braze 284 is formed, as shown. This makes asolid metallurgical and low impedance ground contact to the hermeticflange 120 and to the laser weld cap 278. An electrical connection 282is then made to the ground metallization 194 of the shieldedthree-terminal flat-through EMI/energy dissipating filter 190 therebyproviding a very low impedance RF ground. One can see in FIG. 102 thatground shield plates 194 and 194′ are external for the purposes of thisillustration; however, they could be internal plates as previouslyillustrated.

103 is applicable to many of the illustrated embodiments of the presentinvention and simply illustrates a methodology of having a circuit traceT₁ or T₂ dodge around a via hole V such that it maintains a high surfacearea (to maximize ECA) and remains in electrical isolation. As one cansee in the upper view, circuit trace T₁ can be routed in a circularmanner all around the via hole or it can simply be routed around the viahole. To maximize flat-through capacitance ECA, the upper trace is thepreferred embodiment.

FIG. 104 illustrates an alternative embodiment to FIG. 82 in that it isan octapolar design instead of a quadpolar design. Also, instead ofhaving lead wires for transition to integrated circuit boards, it haswire bond pads 286 for convenient connection of jumper wires to othercircuits.

FIG. 105 is very similar to FIG. 104 except that it illustrates themethodology of breaking up the flex cable portion 192′ of the hybridsubstrate 192 into individual arms/traces for direct electricalconnection to other locations, for example to an IC board, within ageneral electronics module or an AIMD.

FIG. 106 illustrates an in-line octapolar hermetic or non-hermeticterminal 112 with a hybrid substrate 192 of the present inventionexploded away from it, but designed to be mounted to it. One can seethat there are a number of MLCC capacitors 142 that are in series withan embedded inductor meander 158. Wire bond pads 139 are provided at theend for convenient connection of jumper wires to AIMD or otherelectronic device electrical circuits.

FIG. 107 is a manufacturing production flow chart illustrating a verylow cost and a very reliable way to manufacture the present invention.By way of illustration, we will be referring to the particular hybridsubstrate 192 as previously illustrated in FIG. 84. As previouslymentioned, it is highly desirable that during assembly that thissubstrate 192 be laid flat. it can then later be bent into any desiredshape as shown in FIG. 87. The first step is to dispense conductiveepoxy using a robot to achieve the ring of thermal-setting conductiveadhesive 254 as previously described in connection with FIG. 92. This isthen assembled into the hermetic seal 112 and cured at temperaturesranging from 150 to 300 degrees centigrade. The electrical chipcomponents are then robot-loaded either from tape and reels or fromcarrier trays. The chip components can consist of any combination MLCCcapacitors 142, chip inductors 156, diodes 154, bandstop filters, L-Ctrap filters, RFID chips or any other electronic components. These arethen run through an automated soldering operation and cleaning operationwhere they go through an automated optical visual inspection. Theelectrical inspection is also automated. High reliability screening isthen done automatically such as burn in, life testing and the like.Parts are then ready for packaging and shipping.

FIG. 108 illustrates a typical 16-lead glass hermetic seal 112 thatwould be typically found in a cochlear implant. Also shown is a novelhybrid substrate 192 of the present invention which consists of a rigidsection 192″ and a thin flexible section 192′. In this case, the thinflexible section 192′ has been bent over into a 90 degree angle forconvenient attachment to the hermetic seal assembly 112. A number ofMLCC capacitors 142 are shown mounted. Not shown are internal groundshield plates of the present invention. The MLCC's 142 can support twopurposes in this application. Some of the MLCC's 142 are used in serieswith the flat-through capacitor active electrodes, which are also knownin the art as DC blocking capacitors. This is in order to protect bodytissues from excessive electrical stimulation. Also shown are anotherrow of MLCC capacitors 142′ which are generally connected to ground toperform EMI filtering in accordance with the present invention. This isbetter understood by referring to the schematic diagram in FIG. 109.

Referring to the body fluid side of FIG. 109, starting with the topschematic, as we enter into the shielded area Sh, we first encounter theflat-through parasitic capacitances C_(P) that are formed in the presentinvention between embedded ground shields (not shown) and the particularcircuit electrode. We then encounter MLCC_(A) which provides additionallow frequency EMI filtering in accordance with the present invention. Wethen enter MLCC_(D) in series which is a DC blocking capacitor which isplaced in series with the circuit trace. Note that since they are bothshielded, the order of MLCC_(A) and MLCC_(D) can be reversed withoutloss of EMI attenuation or body tissue protection. The purpose of seriesDC blocking capacitor MLCCD is to prevent DC bias from reaching bodytissue and possibly causing damage or necrosis. In fact, these DCblocking capacitors are well known in the art and are generally requiredby regulatory agencies, such as the Federal Food and Drug Administration(FDA).

FIG. 110 illustrates a 5-terminal pin hermetic seal 112 of the presentinvention incorporating four quadpolar lead wires 114-114′ which aredesigned to be connected to leads with electrodes that contact bodytissue. Also shown is a fifth pin known as the RF antenna pin 288. RFdistance telemetry is becoming very popular for AIMDs. In older devices,it was typical that telemetry was performed through embedded coilswithin the AIMED. A close coupled coil was brought up close to the skinover the implant which is also known as a telemetry wand. Signals weresent through this close coupled telemetry field in order to interrogatethe implanted medical device, perform reprogramming and the like. Aproblem with this type of telemetry is that in order to effectivelycouple RF energy through the skin, it had to be very low in frequency(generally below 200 kHz). Because of the low frequency, the datatransmission rate was quite slow. Since modern implantable medicaldevices often have over 4000 programmable functions and also store agreat deal of data such as ECG wave forms, the slow transmission rate isvery frustrating and time consuming for medical personnel. In addition,because of the relatively low coupling efficiency, it is necessary thatthe wand be placed in very close proximity to the implant. It oftentakes a little time to find the “sweet spot” so that one will be able tocommunicate with the AIMD properly. High frequency RF telemetryconsisting of antenna 288 has become very popular and is generallyaccomplished in the 402 MHz (MICS band) or at higher frequencies.Because of the high frequency, energy transmission is very efficient. Itis now possible for a doctor sitting at his desk to interrogate apacemaker patient sitting in a chair across the room. Also because ofthe high frequency, the transmission data transfer rates are muchhigher. In other words, this system has much more bandwidth. However, aparticular problem with this is that we now have a lead wire 288 thatenters the interior of the AIMD which cannot, by definition, be EMIfiltered. The presence of broadband EMI filtering would tend to stripoff the desirable high frequency telemetry signal. Accordingly, it isimportant that this unfiltered antenna wire 288 be shielded and routedin such a way that EMI cannot enter into the active implantable medicaldevice and cross-couple to sensitive circuits.

Referring to FIG. 111, one can see that there is an outer metallicshield assembly 290 formed in an oval (can be any enclosed shape) thatsurrounds all of the terminal pins 114-114′″. This also provides aconvenient location for the mounting of the hybrid substrate 192 of thepresent invention. Shown are MLCC capacitors 142 connected between thecircuit traces and a ground metallization 292. Also shown is a novel lidassembly 294 which is metallic and is used to provide a shieldedcompartment which completely encapsulates or encloses the RF telemetrypin antenna 288. There is a convenient access port 296 shown which wouldbe suitable for connection of a coaxial cable. The outer termination orshield of the coaxial cable would make electrical and mechanicalconnection to the ground shield 290. The interior pin of the coaxialcable would enter inside the cavity formed by the lid assembly 294 andmake electrical connection to the RF telemetry pin at point 288. Afterall of this assembly work, the lid 294 would be attached to housing 290by laser welding, soldering, brazing, conductive adhesives or the like.Another alternative to FIG. 111 would be to manufacture the cavityunderneath the lid 294 sufficiently large to place the requiredelectronic RF module to convert the high frequency RF telemetry signalspicked up by the antenna 288 into digital signals. Then these digitalsignals would be EMI noise free and could be routed through either aconnector pin or through the aperture 296.

FIG. 112 is an alternative embodiment to the structure of FIG. 111,wherein reversed geometry MLCC's 142 are used to provide high frequencyattenuation. In addition, optional ferrite beads 298 are used to furtherimprove high frequency attenuation.

FIG. 113 is a manufacturing flow chart that describes an alternativemethod of manufacturing any of the electronic components of the presentinvention. Monolithic ceramic capacitor manufacturing is well known inthe art. However, a more efficient and cost effective way to do thiswould be to use thick film technology and lay down the components of theshielded three-terminal flat-through EMI/energy dissipating filter 190all at one time all on one hybrid substrate 192. Referring to FIG. 113,you would first condition the substrate for adhesion of the variousdielectric and electrode materials. Then you would print the capacitordielectric or diode materials through multiple print operations. Thereis typically a drying operation between each multiple printingoperation. This can be done literally in as many times (end times) asrequired until one reaches the desired capacitance value, inductancevalue or the like. The thick film component is then typically fired innitrogen at temperatures ranging from 850 to 950 degrees C. This is thenlaminated into a substrate structure. The layers are printed and etchedto form capacitor electrodes and terminations and this is laminated intoa substrate or multi-layer board and stacked up using prior artapplication processes. There are then interconnects using conventionalvias or micro-vias to complete the fabrication again using all prior artprocesses.

The novel hybrid substrate 192 of the shielded three-terminalflat-through EMI/energy dissipating filter 190 of the present inventioncan also be used to mount a variety of sensing circuits to be used inconjunction with external or lead-based sensors. For example, for acardiac pacemaker application, a number of physiologic sensors could bemounted on the novel substrate, including respiration rate sensors,blood pH sensors, ventricular gradient sensors, cardiac output sensors,pre/post cardiac load sensors, contractility sensors, hemodynamics andpressure monitoring sensors. Such components could also be used inconjunction with blood gas or oxygen sensors.

FIG. 114 is an outline drawing of an AIMD such as a cardiac pacemaker.Shown is a metallic, typically titanium, housing 300. It is hermeticallysealed with a laser weld 302 as shown. It has a hermetic seal 112, whichis also laser welded to the titanium housing 300. The housing is alsohermetically sealed by laser weld 302. The hermetic seal 112 has aninsulator 118, which is well known in the prior art, through which leadwires 114-114′″ pass through in non-conductive relationship withconductive housing 300. A typical pacemaker connector block 304 isshown. This can be in accordance with various ISO specifications such asIS-1, DF-1, IS-4 and the like. The female connector block 304 allows forconvenient connection of a lead with a male proximal plug(s), which canbe routed to the appropriate body tissue to be sensed or stimulated. Thelead wires 114 through 114′″ are generally routed to circuit boards,hybrid or integrated circuits or substrates 250 within the activeimplantable medical device housing 300. These can include cardiac sensecircuits, pace circuits and the like. There are also variable impedanceelements 306 and 308 as illustrated on lead wire 114′″. It should benoted that these variable impedance circuit elements would appear on allof the lead wires 114-114′″. They are only shown on lead wire 114′″ tosimplify the drawing. A novel feature is to use the metallic housing ofthe AIMD as a large surface area energy dissipating surface (EDS). Thisis also described in U.S. Provisional Patent Application Nos. 61/144,102and 61/149,833, the contents of which are incorporated herein. Theshielded three-terminal flat-through EMI/energy dissipating filter 190of the present invention is an ideal way to reduce to practice and mountall of the various circuit components as described in U.S. ProvisionalPatent Application Nos. 61/144,102 and 61/149,833. Typically the AIMD isinstalled in a pectoral pocket, an abdominal pocket or in some otherlocation that is not in intimate contact with a body organ. Accordingly,if the housing 300 were to overheat, it would be surrounded by fat andmuscular tissue which is not nearly as sensitive to thermal damage as,for example, cardiac tissue or brain tissue. Also referring back to FIG.114, one can see that for AIMDs, the relative surface area of thehousing 300 is quite large in comparison to the electrode tip at the endof an implanted lead. In other words, it embodies a great deal ofsurface area over which to dissipate the MRI RF energy. Accordingly, thethermal rise will be very low (just a few degrees) as opposed to if theenergy were concentrated over a small area in the electrode tip wherethe thermal rise can exceed 30 or even 60 degrees centigrade.Accordingly, it is a feature of the present invention that the housingof the AIMD be used as an energy dissipating surface optionally andideally working in combination with bandstop filters installed at ornear the distal electrode to tissue interface. In FIG. 114, this energydissipation is represented by the arrow marked EDS. In fact, the energyis being dissipated at all points all around the metallic housing 300 tothe surrounding body fluids and tissues.

FIG. 115 is a close-up view of the variable impedance elements 306 and308 from FIG. 114 located within the housing 300 of the AIMD. Aspreviously mentioned, the variable impedance elements 306 and 308 wouldbe installed on all of the leads that ingress and egress the AIMD. Theground symbol g is shown to indicate that variable impedance element 306is connected through the shielded ground plates of the three-terminalflat-through EMI/energy dissipating filter of the present invention tothe metallic housing 300 of the AIMD. The lead wire lengths are not ofparticular concern since they will be embedded within the novel shieldedthree-terminal flat-through EMI/energy dissipating filter technology ofthe present invention. This is very important because each circuitelectrode of the present invention is shielded such that a very highamplitude electromagnetic energy from MRI cannot re-radiate orcross-couple over to sensitive AIMD circuits (such as pacemaker sensecircuits). The sections of lead wire Si and S2 are kept within theshields 194 and 194′ of the shielded three-terminal flat-throughEMI/energy dissipating filter so that high frequency energy from MRIwill not be reradiated to sensitive AIMD circuits. Ideally, circuitelement 306 would be an MLCC chip 142 which would be bonded right at thepoint of lead wire ingress and egress.

FIG. 116 illustrates that the variable impedance element 306 of FIG. 115can be any type of capacitor (C) element, including MLCC chip capacitors142 and the like. FIG. 117 illustrates that the variable impedanceelement 306 can also be a feedthrough capacitor C 132 as has been notedis in the prior art and illustrated in FIG. 91.

FIG. 118 indicates that variable frequency selective element 306 canalso be an inductor (L) in series with a capacitor (C) also known as aL-C trap filter.

FIG. 119 illustrates that the trap filter of FIG. 118 can be used incombination with either a chip capacitor Cx or equivalent capacitor aspreviously illustrated in FIG. 116 or a feedthrough capacitor asillustrated in FIG. 117. For a pacemaker or an ICD, this would be themost common embodiment. Typical capacitance value for the seriesresonant trap would be 270 nanohenries of inductance and 22 picofaradsof capacitance. This would make the series trap filter series resonantat 64 MHz. It's also important that the designer realize that at acertain frequency, the combination of the trap filter 306 and the EMIfilter Cx will at some point become a parallel resonant bandstop filter.This happens at frequencies at which the trap filter becomes inductive.In other words, at resonance, the inductive reactance cancels out thecapacitive reactance and the impedance of the series trap is essentiallyzero except for its real or resistive losses. However, at frequenciesabove resonance, the inductive reactance term tends to increase anddominate the capacitive reactance term. In other words, at frequenciesabove resonance the series LC trap will tend to look like an inductorwhich could then cause a secondary resonance in parallel with thefeedthrough capacitor Cx. This means that there would be a minordegradation in the overall attenuation to electromagnetic interference.This resonant point should not appear at the frequency of a new andpowerful emitter. Resonance at these emitter frequencies thereforeshould be avoided.

FIG. 120 is essentially the same as FIG. 115 except the focus is now onthe series variable impedance element 308. The use of a series impedanceelement 308 is optional, but highly desirable for AMDs that have sensecircuits.

FIG. 121 indicates that the variable impedance element 308 can be aninductor L as shown. This forms what is known in the art as a singleelement low-pass filter. The inductor element L would freely pass lowfrequencies such as biologic frequencies but would offer a higherimpedance to high frequencies such as those of MRI RF pulse frequencies,cellular telephones and the like.

FIG. 122 illustrates that the variable impedance element 308 can be abandstop filter (BSF) consisting of parallel resonant L-C components asshown. The operation of the bandstop filter has been described in U.S.Patent Application Publication No, US 2007/0112398 A1, the contents ofwhich are incorporated by reference herein.

FIG. 123 illustrates that the optional series impedance element 308 canbe any one of a family of low-pass filters. As previously described inconnection with FIG. 121, this could be a single element low-pass filterconsisting of a single inductor element L, 26 or a single capacitorelement C, 20, 306. This could also be an L filter consisting of aninductor element 308, 26, and a second capacitor 304, 20. Variablereactance frequency selective element 308 could also be a T filter or an.eta. element filter which includes π, LL, five element and thelike-type low-pass filters. As one can see from FIG. 123, theattenuation versus frequency slope increases with increasing number ofcircuit elements. The other desirable effect is by having additionalcapacitors connected to the housing 300 of the AIMD, one createsadditional circuit paths for dissipation of energy to the energydissipating surface EDS. Accordingly, in the preferred embodiment, onewould have one or more a parallel selective frequency element(s) 306acting in cooperation with one or more series frequency reactiveelement(s) 308 as illustrated in FIGS. 115 and 120.

For a description of prior art feedthrough capacitors, one is referredto U.S. Pat. No. 4,424,551 or 5,333,095 or 6,765,779, whereinfeedthrough capacitors having extremely low inductance are installed atthe point of lead wire ingress to an active implantable medical device.For a further description of the L-C trap filter illustrated in FIG.117, one is directed to U.S. Pat. No. 6,424,234 which illustrates verylow inductance (leadless) methods of installing the trap filter at thepoint of lead wire ingress or egress of the AIMD or at any location inthe shielded three-terminal flat-through EMI/energy dissipating filter.

FIG. 124 illustrates a schematic diagram of a series inductorL-capacitor C filter which is commonly known in the industry as an L-Ctrap filter. The trap filter was previously described in FIG. 118.Referring once again to FIG. 124, there is a particular frequency for atrap filter when the capacitive reactance becomes equal and opposite tothe inductive reactance. At this single frequency, the capacitivereactance and the inductive reactance cancel each other out to zero. Atthis point, all one has left is the parasitic resistance R. If oneselects high quality factor (O) components, meaning that they are verylow in resistance, then the trap filter of FIG. 124 ideally tends tolook like a short circuit at its resonant frequency f_(r) between pointsA and B which may comprise connections respectively to lead wires114-114′″ which are connected to active electrodes of the shieldedthree-terminal flat-through EMI/energy dissipating filter 190.

FIG. 125 gives the resonant frequency equation where f_(r), in thiscase, was measured in hertz. Referring once again to FIG. 124, it isvery important that the amount of resistance R be controlled. This isbetter understood by referring to FIG. 126.

FIG. 126 is a graph that illustrates the impedance Z in ohms versusfrequency of the series resonant L-C trap filter of FIG. 124. As one cansee, the impedance is quite high until one reaches the frequency ofresonance f_(r). At this point, the impedance of the series L-C trapgoes very low (nearly zero ohms). For frequencies above or belowresonance f_(r), depending on the selection of component values andtheir quality factor (Q), the impedance can be as high as 100 to 1000 oreven 10,000 ohms or greater. At resonance, the impedance tries to go tozero and is limited only be the amount of parasitic resistance R (FIG.124) that is generally composed of resistance from the inductor L andalso the equivalent series resistance that comes primarily from theelectrode plates of the capacitor C. There is a trade off in properselection of the components that controls what is known as the 3 dBbandwidth. If the resistance is extremely small, then the 3 dB bandwidthwill be narrower. However, this makes the trap filter more difficult tomanufacture. Accordingly, the 3 dB bandwidth and the resistive element Rare preferably selected so that it is convenient to manufacture thefilter and tune it to, for example, 64 MHz while at the same timeproviding a very low impedance R at the resonant frequency. For an idealL-C series resonant trap filter, wherein ideal would mean that theresistance R would be zero, then the impedance at resonance would bezero ohms. However, in this case, the 3 dB bandwidth would be so narrowthat it would be nearly impossible to manufacture. Accordingly, someamount of resistance R is in fact desirable.

FIG. 127 is an impedance versus frequency curve wherein two trap filtershave been installed which are designed to resonate at two differentfrequencies. In this case, the first trap filter consisting of capacitorelement C and inductor element L, is designed to be self-resonant at theRF pulse frequency of a 1.5 Tesla MRI system (64 MHz). A second trapfilter has been installed in parallel consisting of capacitor element C′and inductor element L′ with component values designed to beself-resonant or have been designed such that the trap filter isself-resonant at 128 MHz (the operating frequency of a 3 Tesla MRIsystem). Referring once again to FIG. 127, one can see an optionalbandstop filter BSF consisting of the parallel configuration of inductorLx and capacitor Cx. The purpose of the bandstop filter is to isolatethe two trap filters so that they can work independently. The presenceof the bandstop filter prevents secondary resonances from occurringbecause of the tendency for capacitors C and C′ to appear in parallelalong with inductors L and L′ to appear in parallel. In other words, onegets a smoother double trap response when one uses a bandstop filter toelectrically isolate the L-C traps into separate components at thefrequency of interest.

FIG. 128 is an overall outline drawing showing a cardiac pacemaker 310with endocardial leads implanted into a human heart 314 as shown. Eachlead is bipolar meaning that it contains two lead wires. One can seethat lead 312 is routed into the right atrium and that lead wire 312′ isrouted into the right ventricular apex (RVA). The distal electrodes forthe atrial lead are shown at tip 316 and ring electrode 318. In theright ventricle, the distal electrode tip 316′ is shown in closeproximity to distal ring electrode 318′. As previously mentioned,bandstop filters in accordance with U.S. Pat. No. 7,363,090 would beplaced at or near the distal electrodes 316, 316′ 318, 318′ as needed.Referring to the AIMD housing 310, one can see that there are variableimpedance elements 306 and 308 associated with each one of the leadwires which can be incorporated into the shielded three-terminalflat-through EMI/energy dissipating filter 190.

FIG. 129 is a cross-sectional view of a human head showing a deep brainstimulator electrode 320. Lead wires 312 and 312′ are typically routeddown the back of the neck and into the pectoral region and connected toan AIMD (brain neuromodulator). FIG. 129 is simply to illustrate thatthe properties of the present invention are not limited to cardiacpacemakers, but have wide applicability to a wide range of AIMDs aspreviously described with reference to FIG. 1. The frequency selectivecomponents described in FIG. 128 can be integrated into the shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention in a housing 320 in the skull burr hole which also supportsthe deep brain electrodes, or in the AIMD housing as shown in FIG. 114.

FIG. 130 shows a unipolar lead system 312 for an active implantablemedical device. A unipolar lead system is shown for simplicity. It willbe obvious to those skilled in the art that any number of lead wires 312could be used. In FIG. 130, one will see that this system involves anAIMD and housing 300 attached to unipolar lead wire 312 to a human heart314. At the distal tip or distal end of lead wire 312 is an optionalbandstop filter BSF located at or near the stimulation/sense electrode.The optional bandstop filter BSF located near the distal electrode ismore thoroughly described in U.S. Pat. No. 7,363,090 the contents ofwhich are incorporated herein. The implanted lead 312 has inductive Land resistive R properties along its length. The total inductivereactance of lead 312 in ohms is given by the formula +j.omegal as shownin FIG. 130. As mentioned, the bandstop filter BSF may or may not bepresent. Referring once again to FIG. 130, one can see that on theinterior of the generally metallic housing 300 of the AIMD there arefrequency selective components 306 and 308. These frequency selectiveelements can consist of various arrangements of capacitors, inductorsand resistors or even short circuits as will be more fully described inFIGS. 131 through 133.

FIG. 131 illustrates the lead system of FIG. 130 wherein an L-C trapfilter 306 has been placed inside of housing 300 in a shieldedthree-terminal flat-through EMI/energy dissipating filter assembly ofthe present invention. In this case, Ls and C_(s) have been designed asan L-C trap filter to be resonant at the pulsed RF frequency of the MRIequipment. Therefore, this forms an RF short to the AIMD housing 300which becomes an energy dissipating surface EDS of the inventiondisclosed in U.S. Provisional Patent Application Nos. 61/144,102; and61/149,833. It is desirable that the surface area of the AIMD housing300 be relatively large so that very little temperature rise occurs onsurface 300 as the MRI RF energy is being dissipated.

FIG. 132 is another illustration of the unipolar lead system of FIG.130. In this case, element 306 features a capacitive element C whosecapacitive reactance is given by the equation −j/ωC. In a preferredembodiment, the inductive reactance of the implanted lead would first becalculated (modeled) or measured in ohms. Therefore, the value ofcapacitance could be selected such that the capacitive reactance −j/ωCis equal and opposite in ohms to the inductive reactance of the lead+jωL. In this case, the reactances cancel each other so that one obtainsmaximal energy transfer to the energy dissipating surface 300.

FIG. 133 is similar to the unipolar lead system previously described inFIGS. 130 and 132. In this case, as for FIG. 132, the capacitance valueC has been selected such that the capacitive reactance will be equal andopposite to the inductive reactance of the implanted lead. However, inthis case, the resistances are also balanced. In other words, theresistance R of the implanted lead is equal in value to a discreteresistor Rx placed inside or outside of the housing 300 of the AIMD.Ideally, resistor Rx would be incorporated into the shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention. In this case, maximum power transfer or energy will bedissipated by this discrete resistance Rx as heat. In a preferredembodiment, a thermally conductive but electrically insulative materialwill be placed onto the shielded three-terminal flat-through EMI/energydissipating filter over resistor Rx and to the AIMD housing 300 suchthat maximum energy transfer from resistor Rx will occur. In fact, in apreferred embodiment, resistor Rx shall have a finned high surface areahousing for maximal heat transfer area to the surrounding encapsulant.Referring once again to FIG. 133, one can see that energy is radiatedand conducted from a discrete resistance element Rx shown as EDS. Thisenergy being dissipated turns to thermal (heat) energy. It is desirableto have a relatively large thermal mass located within housing 300. TheAIMD housing 300 then becomes a secondary heat dissipating surface HDS.This thermal energy will be dissipated over the relatively large surfacearea 300 into body fluids and tissues that surround the AIMD. Forexample, in a cardiac pacemaker application, housing 300 would be in apectoral muscle pocket.

Referring back to FIGS. 132 and 133, it is not necessary that thereactances completely cancel, or in the case of FIG. 133, it's notparticularly important that the resistances are exactly equal. In fact,there is a tradeoff between EMI filtering of the input capacitance andexact cancellation of the +jwL component lead system. As it turns out,through actual testing, it is really only important that the impedancegenerally be cancelled in the lead system so that at least the bulk ofthe excess energy from the MRI RF pulse field will be dissipated to thehousing 300 of the AIMD. For example, if one calculates that a 75picofarad capacitor would exactly cancel the inductive reactance of thelead system, one may instead choose to use a 1000 picofarad capacitancefor the flat-through and MLCCs of the shielded three-terminalflat-through EMI/energy dissipating filter. The 1000 picofarad totalcapacitance (C_(P)+C) would still draw a large amount of MRI RF energyfrom the lead system to the housing 300. The reason one would do this,is that a 1000 picofarad capacitor would offer much more effective EMIfiltering to not only the RF pulse frequency (64 MHz or 1.4 Telsa MRsystem), but also for cell phones and other emitters commonly found inthe pace environment.

FIG. 134 illustrates filtered connectors 322 a-322 h that are typicallyused in the military, aerospace, medical, telecommunication and otherindustries. In an EMI filtered connector, such as those typically usedin aerospace, military, telecommunications and medical applications, itis very difficult to install a feedthrough capacitor type planar arrayto the connector housing or back shell without causing excessivemechanical stress to the ceramic capacitor. A number of unique mountingschemes are described in the prior art, which are designs thatmechanically isolate the feedthrough capacitor while at the same timeprovide the proper low impedance ground connection and RF shieldingproperties. This is important because of the mechanical stresses thatare induced in a filtered connector. It is problematic to install arelatively brittle ceramic feedthrough capacitor in a filtered connectorbecause of the resulting mismatch in thermal coefficient of expansion ofthe surrounding materials, and also the significant axial and radialstresses that occur during connector mating.

By definition, connectors come in female and male versions to be matedduring cable attach. The EMI filtering is typically done in either thefemale or the male portion, but usually not both. During the insertionor mating of the connector halves, significant mechanical forces areexerted which can be transmitted to the feedthrough capacitor. Insummary, feedthrough capacitors or discrete capacitors in prior artfiltered connectors involved very expensive mounting techniques. It isnot unusual for the filtered connectors, as illustrated in FIG. 134, tocost hundreds or even thousands of dollars each. The present invention,using shielded three-terminal flat-through EMI/energy dissipating filtertechnology offers equal or even higher performance as compared tofiltered connector planar array feedthrough capacitors but at a greatlyreduced cost and size advantage.

With reference to FIGS. 135 and 136, there is shown a prior art subD-type filtered connector 324 utilizing a planar array feedthroughcapacitor (not shown).

FIGS. 137 and 138 illustrate other types of very common connectors. Inthis case, the prior art connectors 326 shown in FIGS. 137 and 138 arenot filtered. In particular, in FIG. 137, one can see the exposedconnector pins P. It is very common that these pins that protrude into ashielded housing in connection with the mounting of the connector. Asone can see, these pins P can easily be connected to the shieldedthree-terminal flat-through EMI/energy dissipating filter of the presentinvention.

FIG. 139 shows a typical connector assembly 330 with an exploded view ofa shielded three-terminal flat-through EMI/energy dissipating filter 190of the present invention. The shielded three-terminal flat-throughEMI/energy dissipating filter 190 can take any of the forms described inthe present invention. For example, FIG. 141 is taken generally frompartial section 141-141 from FIG. 139. One can see that the shieldedthree-terminal flat-through EMI/energy dissipating filter embodies anMLCC capacitor C,306. FIG. 140 illustrates the connector assembly 330,which can be hermetic or non-hermetic, which has been attached to theshielded three-terminal flat-through EMI/energy dissipating filter 190of the present invention.

From the foregoing, it will be appreciated that the shieldedthree-terminal flat-through EMI/energy dissipating filters 190 of thepresent invention have broad application and may be used with a widerange of connectors, terminals and/or hermetic seals that support leadwires as they ingress/egress into electronic modules or shieldedhousings. The flat-through EMI/energy dissipating filters 190 of thepresent invention provide three-terminal capacitive filtering whilesimultaneously providing shielding of circuits and signals passingthrough the robust high current capability electrodes of theflat-through capacitor. The hybrid substrate 192 forming a majorcomponent of the energy-dissipating filter 190 of the present invention,functions in a very equivalent manner to prior art feedthroughcapacitors in that: its internal ground plates act as a continuous partof the overall electromagnetic shield housing of the electronic deviceor module to physically block direct entry of high frequency RF energythrough the hermetic seal or the equivalent opening for lead wireingress and egress; and, the flat-through EMI/energy dissipating filtereffective shunts undesired high frequency EMI signals off of the leadwire (electrodes) to the overall shield housing where such energy isdissipated in eddy currents resulting in a very small temperature rise.

In its most basic form, the shielded three-terminal flat-throughEMI/energy dissipating filter comprises an active electrode platethrough which a circuit current passes between a first terminal and asecond terminal, and a plurality of shield plates substantiallyenveloping the active electrode plate, wherein the shield plates arecollectively coupled to a grounded third terminal. More particularly,the plurality of shield plates include a first shield plate on a firstside of the active electrode plate, and a second shield plate on asecond side of the active electrode plate opposite the first shieldplate.

Although several embodiments of the invention have been described indetail for purposes of illustration, various modifications of each maybe made without departing from the spirit and scope of the invention.Accordingly, the invention is not to be limited, except as by theappended claims.

WWhat is claimed is:
 1. A ground path for an EMI/energy dissipatingfilter assembly for an active implantable medical device, the groundpath comprising: a) an electrically conductive ferrule comprising aferrule opening, wherein the ferrule is configured to be attachable toan opening in a housing of an active implantable medical device (AIMD);b) an insulator at least partially residing in the ferrule opening,wherein the insulator is hermetically sealed to the ferrule, and whereinat least one insulator passageway extends through the insulator; c) aconductive active lead wire hermetically sealed in the at least oneinsulator passageway; d) a circuit board residing adjacent to theinsulator, wherein the circuit board comprises at least one circuitboard ground plate disposed on or within the circuit board substrate; e)a filter capacitor disposed on or adjacent to the circuit board, thefilter capacitor comprising a filter capacitor dielectric supporting atleast one active electrode plate interleaved in a capacitiverelationship with at least one ground electrode plate, wherein an activemetallization is electrically connected to the at least one activeelectrode plate, and a ground metallization is electrically connected tothe at least one ground electrode plate; f) a ground path electricallyextending between the ground metallization of the filter capacitor andthe ferrule, wherein the ground path comprises at least one conductiveground pin electrically and mechanically connected to the ferrule, andwherein the ground path comprises the ground plate being electricallyconnected to both the conductive ground pin and the ground metallizationof the filter capacitor; and g) an active electrically conductivecircuit board path extending from the active lead wire to the activemetallization of the filter capacitor.
 2. The ground path of claim 1,wherein the at least one conductive ground pin is electrically andmechanically connected to the ferrule by one of a first gold braze or alaser weld.
 3. The ground path of claim 2, wherein the first gold brazeand the at least one conductive ground pin at least partially reside inat least one of a ferrule countersink or ferrule counterbore.
 4. Theground path of claim 1, wherein the filter capacitor is a two-terminalor a three-terminal capacitor.
 5. The ground path of claim 4, whereinthe three-terminal capacitor comprises a flat-through capacitor or afeedthrough capacitor.
 6. The ground path of claim 4, wherein thetwo-terminal or three-terminal capacitor comprises at least one of amonolithic ceramic, a stacked film, tantalum, electrolytic, or aluminumelectrolytic.